Case Report: Solid variant of papillary thyroid carcinoma in a young adult with Turner syndrome with chronic thyroiditis.

Turner syndrome is associated with an increased risk of developing several neoplasms. In particular, a clinical feature of Turner syndrome with chronic thyroiditis implies a relationship with thyroid malignancies. We report a very rare case of a solid variant of papillary thyroid carcinoma that was identified during a follow-up of chronic thyroiditis in a 22-year-old woman with Turner syndrome. The patient had no notable history of radiation exposure. No genetic mutations relating to the occurrence of the solid variant of papillary thyroid carcinoma, including RET/PTC rearrangements and mutations in the BRAF or RAS, were detected by a gene panel test, namely, the Oncomine™ Dx Target test. To the best of our knowledge, this is the first report of a solid variant of papillary thyroid carcinoma in a young adult with Turner syndrome with chronic thyroiditis. Our case suggests that in patients with Turner syndrome, there may be different pathogeneses from those previously reported, including exposure to radiation or known genetic mutations for the development of a solid variant of papillary thyroid carcinoma.

Solid variant of odontogenic keratocyst in a 22-year-old man: Report of a case.

Key Clinical Message: In conclusion, we can focus on histologic features such as stellate reticulum, reverse polarization of basal cell layer nuclei, and luminal lamellated keratinization as distinguishing factors of ameloblastoma and SKCO. If there is any clinically doubt, molecular testing could be helpful. Abstract: "Solid odontogenic keratocyst" is a rare variant of odontogenic keratocyst, which usually involves mandible. This case was presented as a unique variant of odontogenic keratocyst in an unusual site of left maxilla with extension to the maxillary sinus.

Histological Variants of Papillary Thyroid Cancer in Relation to Clinical and Morphological Parameters and Prognosis.

The correlation of histological features of papillary thyroid cancer with clinical and morphological prognostic factors and cause-specific mortality was analyzed in a case-control study within a cohort of patients from the Altai Regional Oncology Center (25 cases with lethal outcome and 64 follow-up controls). Significant variability was revealed in the histological structure of papillary thyroid cancer with the prevalence of classic (62%) and less frequent follicular (19%), tall cell (8%), and solid (7%) variants. In comparison with the classic variant, the solid variant was more often associated with male sex and large tumor size; follicular and tall cell variant was associated with more frequent metastases to regional lymph nodes; follicular and solid variants were associated with an increased proportion of cases with disease stages III-IV. The main differences reflecting the effect of histological factor on the disease outcome were associated with the solid variant of papillary thyroid cancer that was detected in 21% of lethal cases and only in 2% of control subjects. The detection of this variant can be of importance as an additional prognostic factor of the postoperative survival in papillary thyroid cancer.

Synchronous polyostotic solid variant of aneurysmal bone cyst involving thoracic vertebrae and harboring a novel AHNAK::USP6 gene fusion. A case report and review.

Aneurysmal bone cyst (ABC) is a benign bone neoplasm that usually affects the metaphysis of long bones and the posterior elements of vertebral bodies. The rearrangement of USP6 gene is present in most of primary ABC cases. Synchronous polyostotic presentation is extremely rare. All of the eight reported cases in literature have a classic ABC histomorphology, including dilated-blood filled cystic spaces separated by fibrous septa and composed of variably cellular bland fibroblasts with scattered osteoclast-like giant cells and reactive new bone formation. Herein, we report a case of a 29-year-old female with a synchronous polyostotic solid variant of ABC involving her T7-T11 posterior elements of her thoracic vertebrae with a novel AHNAK::USP6 fusion, detected by next-generation sequencing (NGS). This case is distinguished by its synchronous polyostotic presentation, solid rather than classic ABC morphology and novel AHNAK::USP6 fusion, which has not been previously reported in ABC or in any mesenchymal bone tumor.

Incidental Solitary Adrenal Metastasis as the Initial Manifestation of a Solid Variant of Papillary Thyroid Carcinoma, With Emphasis on Pathologic Diagnosis and Clinical Management.

Objective: Distant metastases from papillary thyroid carcinoma (PTC) are relatively rare and may be associated with a poor prognosis. The adrenal gland is a highly unusual site of metastasis in the natural course of PTC. Herein, we describe a case of an incidentally detected metastatic solid variant of PTC in the adrenal gland of an asymptomatic patient as the initial presentation. Case Report: A 67-year-old male patient was evaluated for a 4.7-cm adrenal incidentaloma discovered during a workup for nephrolithiasis. Biochemical evaluation revealed a nonfunctioning adrenal mass. The patient underwent adrenalectomy, which revealed metastatic PTC. A subsequent thyroid ultrasound revealed an isthmic nodule. Fine needle aspiration of the nodule was cytologically suspicious for a follicular neoplasm, and gene expression analysis revealed an HRAS c.182A>G sequence variation. The patient subsequently underwent total thyroidectomy, which revealed a 1.2-cm solid variant of PTC in the thyroid isthmus. Postoperatively, the patient underwent radioactive iodine ablation. Discussion: Our case illustrates an exceedingly rare and challenging situation-a metastatic solid variant of PTC in the adrenal gland of a patient with no prior history of PTC. When confronted with a PTC in the adrenal gland in the absence of a previously identified primary tumor, our experience suggests that the next step in management should be total thyroidectomy followed by radioactive iodine ablation. Conclusion: A solid variant of PTC is a rare cause of an incidentally detected adrenal lesion. Multidisciplinary care team coordination is essential for accurate diagnosis and treatment plan formulation.

The solid variant of papillary thyroid carcinoma: a multi-institutional retrospective study.

AIMS: The definition of papillary thyroid carcinoma, solid variant (PTC-SV) varies from >50% to 100% of solid/trabecular/insular growth (STI). We aimed to identify prognostic factors and to establish an appropriate STI cutoff for PTC-SV in this multi-institutional study of 156 PTCs with STI. RESULTS: Nodal metastases were seen in 18% and were associated with a higher percentage of papillary and STI. When substratified by infiltration/encapsulation status, the STI percentage did not impact the risk of nodal metastasis. pN1 stage was seen in 51% of infiltrative tumours and 1% of encapsulated lesions. Overall, PTC with STI had an excellent prognosis. The 10-year disease-free survival (DFS) was 87% in the entire cohort, 94% in encapsulated lesions, and 76% in infiltrative tumours. The STI percentage did not impact DFS. Fifty-four patients had noninvasive encapsulated lesions with 2-100% STI. None developed recurrence. Encapsulated lesions were enriched with RAS mutations (54%), whereas infiltrative lesions lacked RAS mutations (4%). The BRAF V600E mutation was an infrequent event, being seen in 11% of the entire cohort. CONCLUSION: In PTC with STI, the determining factor for nodal metastasis and DFS is the encapsulation/infiltration status rather than the STI percentage. Encapsulated noninvasive tumours with STI follow an indolent course with a very low risk of nodal metastasis and recurrence. Overall, PTC with STI has an excellent prognosis, with a 10-year disease-specific survival (DSS) and DFS of 96% and 87%, respectively. Therefore, the classification of SV-PTC as an aggressive PTC subtype may be reconsidered.

Solid-variant aneurysmal bone cysts in the craniofacial skeleton: the role of genomic analysis.

BACKGROUND: Solid variant aneurysmal bone cysts (SVABCs) are a rare but well-described subtype of ABCs. While classic ABCs are readily identified radiographically, SVABCs lack these characteristic radiographic features and thus have a wide differential diagnosis on presentation (including Ewing sarcoma, Langerhans cell histiocytosis, osteosarcoma, metastasis, and giant cell tumor). Genomic/molecular analyses are often necessary for the diagnosis of SVABCs, with USP6 rearrangements being a characteristic finding. We present two cases in which genomic analysis was critical in the diagnosis of SVABCs and revealed unique gene fusions that may provide insight into SVABC pathogenesis. CASE DESCRIPTIONS: Two 13-year old male children presented to our institution with new mass lesions involving the craniofacial skeleton. Magnetic resonance imaging (MRI) in both cases revealed predominantly solid, avidly enhancing masses, one of the squamous portion of the temporal bone, and the other arising from the sphenopalatine foramen with extension into the ipsilateral maxillary and ethmoid sinuses. Histopathology displayed predominantly solid morphology, and next generation sequencing (NGS) revealed a FAT1-USP6 gene fusion in the temporal lesion, and a MIR22HG-USP6 gene fusion in the maxillofacial lesion, the latter of which was not identified on fluorescence in situ hybridization (FISH). These findings were most consistent with a diagnosis of SVABC in each case. CONCLUSIONS: These two cases highlight novel gene fusions in atypically located SVABCs and emphasize the ability of NGS to more accurately and consistently identify USP6 gene fusions, particularly in SVABCs that may otherwise be indistinguishable from alternative pathologies.

Solid variant of papillary thyroid carcinoma: An analysis of 28 cases with current literature.

INTRODUCTION: Solid variant papillary thyroid cancer (SVPTC) is a rare variant of papillary thyroid carcinoma (PTC) and its prognostic value is still unclear. Therefore, we re-evaluate the histopathological and clinicopathological features of 28 patients with SVPTC in the light of current literature. MATERIAL-METHODS: Of the 1308 cases were previously diagnosed with PTC and 28 (2,1%) of them which had been diagnosed with SVPTC were re-evaluated retrospectively. RESULTS: Of the 28 patients with SVPTC, 85.7% were female, mean age was 45.18 years and mean tumor diameter was 2.96 cm. Microscopically; tumors had a solid growth pattern amounting to at least 50.0% of the tumor volume. In all cases the tumor cells had characteristic nuclear features of conventional PTC. 11 patients had multifocal tumors, extrathyroidal extension was present in 4 patients and vascular invasion was observed in 7 cases. Regional lymph node metastases were noted in 2 (7.1%) cases at the time of diagnosis. One patient died because of locally advanced disease. Another patient is alive with lung metastases after 48 months from the initial surgery. There was no evidence of local recurrence in other patient. CONCLUSIONS: SVPTC is a rare variant of PTC that should be considered in the differential diagnosis of tumors which show a solid/trabecular growth pattern in the thyroid. It has poor prognostic features such as widespread angioinvasion, extrathyroidal extention, lymph node metastasis, and distant organ metastasis. Multicenter studies involving large number of cases are needed to reveal the prognostic significance of SVPTC, with standardized diagnostic criteria.

Should the solid variant of odontogenic keratocyst and keratoameloblastoma be classified as the same entity? A clinicopathological analysis of nine cases and a review of the literature.

The solid variant of odontogenic keratocyst (SOKC) is an extremely rare odontogenic lesion, which remains poorly defined even in the 2017 World Health Organization odontogenic tumour classification. It is difficult to distinguish between SOKC and so called keratoameloblastoma (KAB), both rare lesions that have similarities in clinical, histological and biological characteristics. Here, we report clinicopathological data and results of molecular analysis of nine cases with a literature review. First, they were compared to previously reported cases of SOKC and/or KAB, and many overlaps were found in clinical and pathological characteristics. Second, we performed PCR analysis for BRAF V600E mutation. Although ameloblastoma-like epithelia were often encountered, none exhibited BRAF V600E mutation, which has been reported to occur frequently in ameloblastomas but not in odontogenic keratocysts (OKCs). One of two cases of SOKC in the present series from which fresh frozen tissue specimens were available was found to harbour PTCH1 mutations, indicating that these were more likely to be a subtype of OKC. Moreover, we also examined the differences between SOKC and primary intraosseous carcinoma (PIOC) with regard to the expression of cytokeratins (pan-CK, CK5/6, CK7, CK8/18, CK10, CK14 and CK19), p53 and Ki-67. The proportions of p53-and Ki-67-positive cells were significantly higher in PIOC than in SOKC. These findings suggest that immunostaining for p53 and Ki-67 would be useful to differentiate between SOKC and PIOC. We also conducted a review of SOKC and KAB cases reported in the English language literature.

Central angioleiomyoma of the mandible: A rare entity.

The leiomyoma is a benign smooth-muscle neoplasm commonly found in the female genital tract, gastrointestinal tract, or skin. Leiomyomas of the oral cavity are unusual. Oral leiomyomas are uncommon due to the paucity of the smooth muscle in the mouth (except in blood vessels) and thus the involvement of jaw bones is extremely rare. Leiomyomas have been classified as solid angiomyoma, angioleiomyoma (vascular leiomyoma), and epithelioid variants. Angioleiomyomas are benign mesenchymal tumors derived from smooth muscle, which rarely occur in the oral cavity. Malignant transformation probably does not occur but careful histopathologic examination is still necessary to differentiate these benign lesions from their malignant counterparts due to different prognosis. Although uncommon in the maxilla and mandible, they should be included in the differential diagnosis of radiolucent lesions of jaw bones. An extensive search of literature was carried out on the Medline-PubMed and Google Scholar database using the keywords such as leiomyoma, angioleiomyoma, jaw bones, maxilla, mandible, intra-osseous to thoroughly search and collect all the reported cases of intraosseous leiomyoma (but our search was not limited to these terms only). To the best of our knowledge, only 23 cases of intraosseous leiomyomas have been reported so far in the jaw bones, among which only 8 belonged to angioleiomyomas. Herein, we report the 9th case of intraosseous angioleiomyoma, one of the variants of leiomyoma and overall 24th intraosseous leiomyoma in a 6-year-old female child, together with conventional histopathologic and immunohistochemical findings.

Papillary Thyroid Cancer-Aggressive Variants and Impact on Management: A Narrative Review.

INTRODUCTION: Aggressive variants of papillary thyroid cancer (PTC) have been described with increasing frequency. These variants include diffuse sclerosing variant, tall cell variant, columnar cell variant, solid variant, and hobnail variant. METHODS: We have performed a review of the more aggressive variants of PTC with respect to main characteristics, histological and molecular features, and the consequences that the knowledge of these variants should have in the treatment of the patients. RESULTS: At the present time, we do not know the prognostic value of these aggressive PTC variants. The extent of the surgical treatment and adjuvant therapy necessary should be decided on the basis of the extent of the tumor at presentation and the opinion of experienced clinicians. CONCLUSION: These aggressive variants should be known by clinicians, to avoid underdiagnosis, and treated according to the latest recommendations in the literature.

Solid variant of papillary thyroid carcinoma: an under-recognized entity.

Solid variant of papillary thyroid carcinoma (SVPTC) is a rare morphological variant of papillary thyroid carcinoma (PTC). SVPTC is histologically characterized by predominant solid, trabecular and insular nests of tumor cells while cytological features of PTC such as nuclear grooves and nuclear inclusions are preserved. In fine needle aspiration cytology smears, tumor cells of SVPTC may be presented in cohesive, syncytial or trabecular clusters accompanied by some discohesiveness in the absence of necrosis. Although SVPTC and poorly differentiated thyroid carcinoma (PDTC) share similar histological findings of solid nests, SVPTC can be differentiated from PDTC in the lack of tumor necrosis, severe nuclear atypia, and a higher mitotic index. Immunohistochemical expression of CK19 and HBME-1, common markers of PTC, is decreased in solid nests of SVPTC. In pediatric patients exposed to radiation after the Chernobyl nuclear accident, there was a higher prevalence of SVPTC with RET/PTC3 type rearrangement. BRAF mutations are also reported in a small number of adult patients with SVPTC without any prior radiation exposure. Patients with SVPTC may have a slightly higher incidence of metastasis and recurrence of the tumor compared to conventional PTC, although overall survival rate is comparable. In this article, the current knowledge of SVPTC will be reviewed and discussed with an emphasis on the histopathological feature.

Solid variant ABC of long tubular bones: A diagnostic conundrum for the radiologist.

Solid variant of aneurysmal bone cyst (sABC) is an extremely rare, reactive and non-neoplastic osseous lesion. On imaging it presents as a diaphyseal aggressive, eccentrically placed lytic and expansile lesion. However, differentiating this entity from the other possible malignant differentials is confounded by the histopathology mimicking several commoner lesions. We describe the distinctive MRI features of sABC of long bones from a series of four cases and briefly review the literature. We hope this review will educate all radiologists about this rare entity increasing their diagnostic confidence while formulating differentials for similar appearing lesions.

Xp11.2 translocation renal cell carcinoma with SFPQ/PSF-TFE3 fusion gene: A case report with unusual histopathologic findings.

Xp11.2 translocation renal cell carcinoma (Xp11tRCC) is a subtype of renal cell carcinoma (RCC) characterized by chromosomal rearrangement of the region harboring the transcription factor for immunoglobulin heavy-chain enhancer 3 (TFE3). Xp11tRCCs comprises 20% to 40% of RCCs of children and adolescents and is generally associated with good prognosis. However in adult, the incidence of this tumor is relatively low (1% to 4%), suggesting a more aggressive course. TFE3 gene is fused by translocation to numerous partner genes, and definitive molecular characteristics can be difficult to verify. In this case report, we presented a case of Xp11tRCC with the SFPQ/PSF-TFE3 chimeric gene. The fusion gene was detected by 5'-rapid amplification of cDNA ends (5'RACE). The tumor was found to be in an advanced stage with multiple lymph node metastases. The histological characteristics of the tumor were different from those of XP11tRCC with other more frequently detected fusion genes.

Atypical presentation of a solid-variant orbital aneurysmal bone cyst with a literature review.

INTRODUCTION: Aneurysmal bone cysts (ABCs) are rare, rapidly expansile, benign, vascular lesions capable of causing local bone destruction. The majority of cases present as multi-cystic lytic lesions (with solid-variant ABCs representing<10% of all presentations) of the long bones or vertebrae, rarely occurring in the head/neck region. CLINICAL CASE: A 44-year-old female presented with nine days of worsening pain, ptosis and proptosis in the right eye. CT and MR imaging revealed a 3.2cm extra-axial multiloculated right frontal lobe mass in the orbit with fluid-fluid levels secondary to layering of solid blood components. A right craniotomy was performed and the lesion was resected piecemeal with subsequent high speed burring to remove residual tissue. Histological evaluation revealed spindle and giant cell infiltration of the bone without vascular channels. Based on these findings, the lesion was diagnosed as a solid-variant orbital ABC without paranasal sinus involvement. The patient recovered fully with no residual symptoms. CONCLUSION: This case report details a rare presentation of ABC (solid-variant presenting outside of the vertebrae/long bones) with discussion concerning possible treatment modalities and guidance for follow-up.

Cytopathology of Solid Variant of Papillary Thyroid Carcinoma: Differential Diagnoses with other Thyroid Tumors.

OBJECTIVES: Solid variant of papillary thyroid carcinoma (SVPTC) is rare, differing from classical PTC (cPTC) in architecture and outcome. We evaluated the cytomorphology of SVPTC cases to assess the feasibility of a preoperative diagnosis. STUDY DESIGN: SVPTC cases were evaluated for architecture, nuclear features, and Bethesda category and were compared with noninvasive follicular thyroid neoplasm with papillary-like nuclear features/follicular variant of PTC (NIFTP/FVPTC), cPTC, and poorly differentiated thyroid carcinoma (PDTC). RESULTS: Nine SVPTCs, 29 NIFTP/FVPTCs, 12 cPTCs, and 4 PDTCs were included. The predominant architecture in most SVPTCs was solid fragment, which is helpful in differentiating them from NIFTP/FVPTC (p < 0.001) and cPTC (p = 0.006) but not from PDTC. The presence of microfollicles led to misinterpretation as NIFTP/FVPTC/follicular neoplasm in 4 patients. All but 1 SVPTC showed diffuse nuclear features. Intranuclear pseudoinclusions (INIs) were seen in 67% of SVPTCs as compared to 83% of cPTCs, 14% of NIFTP/FVPTCs (p = 0.005), and none of PDTCs. SVPTC cases were commonly (78%) categorized as intermediate/suspicious. CONCLUSIONS: The presence of solid fragments and lack of true papillae are helpful in differentiating SVPTC from cPTC. Solid fragments, trabeculae, the extent of nuclear features, and INIs should be looked for in cases with prominent microfollicles for distinguishing SVPTC from NIFTP/FVPTC. None of the features were helpful in differentiating SVPTC from PDTC.

[DICER1 mutated, solid/trabecular thyroid papillary carcinoma in an 11-year-old child]. / Carcinome papillaire thyroïdien variante solide/trabéculaire avec mutation DICER1 chez une enfant de 11 ans.

We report the case of an 11-year-old patient diagnosed with a solid variant of papillary thyroid carcinoma. Papillary thyroid carcinoma (PTC) is the most common thyroid cancer, representing 80-90% of all newly diagnosed thyroid cancers. Among the many variants described, solid/trabecular variant of papillary thyroid carcinoma is a rare entity and account for 3% of thyroid cancers. It is more common in children and young adults, and it is seen in higher proportion in post radiation papillary thyroid carcinoma cases. Histologically, solid variant papillary carcinoma is characterized by a predominantly solid, trabecular or insular growth pattern, and the presence of cytological features typical of PTC. Its main differential diagnosis is poorly differentiated thyroid carcinoma. It has a less favorable prognosis than the classical papillary type, with a higher risk of distant metastasis, extrathyroidal extension and lympho-vascular invasion. It is associated with a slightly lower long-term survival in adult cases, but not in children. The management of solid variant PTC includes surgery, associated or not with postoperative radioiodine ablation, according to the aggressiveness criteria. Our patient had a DICER1 somatic mutation. Carriers of germline DICER1 mutations are predisposed to a rare cancer syndrome, the DICER1 syndrome, with a higher risk of numerous tumors and infrequently differentiated thyroid carcinomas.

Loss of One or Two PATZ1 Alleles Has a Critical Role in the Progression of Thyroid Carcinomas Induced by the RET/PTC1 Oncogene.

POZ/BTB and AT-hook-containing zinc finger protein 1 (PATZ1) is an emerging cancer-related gene that is downregulated in different human malignancies, including thyroid cancer, where its levels gradually decrease going from papillary thyroid carcinomas (PTC) to poorly differentiated and undifferentiated highly aggressive anaplastic carcinomas (ATC). The restoration of PATZ1 expression in thyroid cancer cells reverted their malignant phenotype by inducing mesenchymal-to-epithelial transition, thus validating a tumor suppressor role for PATZ1 and suggesting its involvement in thyroid cancer progression. Here, we investigated the consequences of the homozygous and heterozygous loss of PATZ1 in the context of a mouse modeling of PTC, represented by mice carrying the RET/PTC1 oncogene under the thyroid specific control of the thyroglobulin promoter RET/PTC1 (RET/PTC1TG). The phenotypic analysis of RET/PTC1TG mice intercrossed with Patz1-knockout mice revealed that deficiency of both Patz1 alleles enhanced thyroid cancer incidence in RET/PTC1TG mice, but not the heterozygous knockout of the Patz1 gene. However, both RET/PTC1TG;Patz1+/- and RET/PTC1TG;Patz1-/- mice developed a more aggressive thyroid cancer phenotype-characterized by higher Ki-67 expression, presence of ATCs, and increased incidence of solid variants of PTC-than that shown by RET/PTC1TG; Patz1+/+ compound mice. These results confirm that PATZ1 downregulation has a critical role in thyroid carcinogenesis, showing that it cooperates with RET/PTC1 in thyroid cancer progression.

Prognostic importance of solid variant papillary thyroid carcinoma: A systematic review and meta-analysis.

BACKGROUND: Solid variant papillary thyroid carcinoma (SVPTC) is a rare variant of papillary thyroid cancer (PTC) and its prognostic value is still unclear. The purpose of this systematic clinical review and meta-analysis is to investigate the prognostic value of SVPTC in comparison with classical PTC (cPTC). METHODS: Four electronic databases, including PubMed, Scopus, Web of Science, and Virtual Health Library, were searched in June 2017. Extracted data were pooled into odds ratio (OR) or hazard ratio (HR) and their corresponding 95% confidence interval (CI) using the random-effect model. RESULTS: From 1439 articles, we finally included 11 studies with 205 SVPTCs for meta-analysis. Overall, SVPTC manifested a significantly higher risk for vascular invasion, tumor recurrence, and cancer mortality as compared to cPTC. The genetic profile of SVPTC was also distinct from that of cPTC. CONCLUSION: A case of SVPTC should be regarded as an aggressive variant of PTC because of a higher risk for tumor recurrence and mortality.

Solid Variant of Aneurysmal Bone Cyst of the Temporal Bone.

OBJECTIVES: Aneurysmal bone cysts (ABC) are benign, rapidly growing osteolytic lesions. Solid variant of ABC (SVABC) is a rare subtype of ABC that has not been reported in the temporal bone. METHODS: We report the case of a 6-year-old boy presenting with a slowly enlarging bony protuberance over the right zygomatic/malar eminence region. Computed tomography and magnetic resonance imaging demonstrated a 2.6 × 5.8 × 5.1 cm temporal bone mass involving the right mastoid, petrous, and temporal squamosal calvarium, with extradural intracranial extension to the middle cranial fossa. RESULTS: The patient underwent preoperative embolization of feeder arteries followed by combined neurosurgical and neurotologic resection. Histopathology revealed characteristic ABC features with interspersed areas of intralesional osteoid formation. CONCLUSION: Solid variant of ABCs are rare lesions of the skull base that present a diagnostic challenge given their unique radiographic and histologic features. Thorough cytogenetic evaluation is warranted to rule out potential malignant secondary causes. Early surgical resection is essential due to the risk of intracranial extension. This is the first report of ABC of any type with concurrent involvement of the squamous, mastoid, and petrous portions of the temporal bone and the first report of SVABC of the temporal bone.