Prevalence of the EGFR T790M and other resistance mutations in the Australian population and histopathological correlation in a small subset of cases.

We sought to review the prevalence of EGFR T790M and other EGFR mutations associated with either proven or probable tyrosine kinase inhibitor (TKI) resistance in the Australasian lung cancer population and to perform histopathological correlation in a subset of cases. Retrospective statistical analysis was performed on a set of targeted lung cancer gene mutation tests (FIND IT gene panel) performed at Sonic Healthcare during 2018 and early 2019. A total of 1833 lung adenocarcinoma tumour samples underwent somatic mutation testing. EGFR mutations were found in 28% (n=514) of patients, in whom 9.3% (n=48) T790M mutations were present (always combined with other EGFR mutations) and 4.8% (n=25) exon 20 insertions were found. We also compared the prevalence of EGFR mutations identified in our population with that of the four largest publicly available lung cancer cohorts (total n=576 samples). Finally, a subset of 38 samples of primary/and or metastatic lung adenocarcinomas from 23 patients, including five with serial biopsies, underwent detailed morphological analysis. No reproducible morphological correlates were found to be associated with T790M, exon 20 resistance mutations or rarer co-occurring EGFR mutations. Although this may be subject to referral bias towards patients with resistant disease, the incidence of EGFR and T790M mutations is higher in this series from an Australasian population than in other similar publicly available lung adenocarcinoma cohorts. We conclude that histopathological features cannot be used to predict the acquisition of EGFR resistance.

Primary breast cancer of the vulva: A case report and literature review.

An elderly lady presented with a 2-year history of intermittent vaginal bleeding and later the development of a vulvovaginal mass. A core biopsy histology specimen from the mass and the left inguinal lymph node was suggestive of metastatic adenocarcinoma of breast origin. No breast lesion was detected on mammography, and axillary nodes were negative. The histopathologic features and the expression of GATA3, cytokeratin (CK)7, mammaglobin staining and estrogen and progesterone receptors led to a diagnosis of breast cancer originating from the ectopic mammary tissue in the vulva. Given the rarity of these lesions, and the lack of standard treatment guidelines, the management of the patient was extrapolated from the established breast cancer treatment guidelines. Radiotherapy and chemotherapy followed by hormone therapy with aromatase inhibitor were administered to this patient in the metastatic setting with good palliation.

Immunohistochemistry for SDHB triages genetic testing of SDHB, SDHC, and SDHD in paraganglioma-pheochromocytoma syndromes.

Up to 30% of pheochromocytomas and paragangliomas are associated with germline RET, Von Hippel-Lindau (VHL), neurofibromatosis type I (NF1), and succinate dehydrogenase subunits (SDHB, SDHC, and SDHD) mutations. Genetic testing allows familial counseling and identifies subjects at high risk of malignancy (SDHB mutations) or significant multiorgan disease (RET, VHL, or NF1). However, conventional genetic testing for all loci is burdensome and costly. We performed immunohistochemistry for SDHB on 58 tumors with known SDH mutation status. We defined positive as granular cytoplasmic staining (a mitochondrial pattern), weak diffuse as a cytoplasmic blush lacking definite granularity, and negative as completely absent staining in the presence of an internal positive control. All 12 SDH mutated tumors (6 SDHB, 5 SDHD, and 1 SDHC) showed weak diffuse or negative staining. Nine of 10 tumors with known mutations of VHL, RET, or NF1 showed positive staining. One VHL associated tumor showed weak diffuse staining. Of 36 tumors without germline mutations, 34 showed positive staining. One paraganglioma with no known SDH mutation but clinical features suggesting familial disease was negative, and one showed weak diffuse staining. We also performed immunohistochemistry for SDHB on 143 consecutive unselected tumors of which 21 were weak diffuse or negative. As SDH mutations are virtually always germline, we conclude that approximately 15% of all pheochromocytomas or paragangliomas are associated with germline SDH mutation and that immunohistochemistry can be used to triage genetic testing. Completely absent staining is more commonly found with SDHB mutation, whereas weak diffuse staining often occurs with SDHD mutation.

Primary cutaneous lymphoblastic lymphoma in children: series of eight cases with review of the literature.

AIM: Primary cutaneous lymphoblastic lymphoma is a rare but well recognised tumour predominantly of childhood. In this study we examine eight cases of cutaneous lymphoblastic lymphoma in children, which is the largest series to date of tumours confined to the skin with or without local lymph nodes (stage I or II) but without systemic disease at diagnosis. METHODS: The clinical history and histology from the eight cases were reviewed together with a panel of immunohistochemical stains to confirm lineage and diagnosis. RESULTS: Seven of the eight cases were confirmed as B-lymphoblastic lymphoma (B-LBL) of the skin, with the eighth case representing a CD4+/CD56+ plasmacytoid dendritic cell tumour. The cases were all stage I or II, and all patients received systemic chemotherapy after full staging investigations to exclude systemic disease at diagnosis. All patients remained in complete remission at the time of last follow-up of between 3 and 9 years from diagnosis. CONCLUSIONS: Lymphoblastic lymphoma may present primarily in the skin without systemic manifestation, with the majority of such cases representing B-LBL. A rare case of childhood CD4+/CD56+ plasmacytoid dendritic cell tumour with similar blastic morphology is also described. Full staging investigations are mandatory at diagnosis to exclude systemic disease. Cases confined to stage I or II at diagnosis carry an excellent prognosis with appropriate systemic chemotherapeutic treatment.