Incidentaloma on Staging CT Revealed to Be Breast to Renal Tumour-to-Tumour Metastasis.

Tumour-to-tumour metastases (TTM) are a rare phenomenon in which a primary tumour has metastasised within another distant primary tumour. We present the case of a 63-year-old female who presented with right-sided breast cancer. An incidental left-sided renal mass was detected on staging CT of the thorax, abdomen, and pelvis (CT-TAP). The patient had no evidence of metastases below the diaphragm. Histology following a radical left nephrectomy revealed metastatic breast cancer within a renal cell carcinoma (RCC). The patient underwent chemotherapy and surgery for right-sided breast cancer. Follow-up imaging demonstrated the metastatic spread of the breast cancer. This is an unusual case of TTM from breast to an initially occult RCC primary.

Cerebral meningioma associated with extensive calvarium osteolysis and presumed intratumoral carcinoma metastasis in a cat.

Case summary: A 10-year-old male neutered domestic shorthair cat presented with a 3-month history of weight loss, dysorexia and lethargy. Neurological examination revealed decreased mentation, absent menace response bilaterally and proprioceptive deficits affecting all four limbs; these findings were consistent with a forebrain disorder. Brain CT revealed an extensive asymmetric permeative osteolysis destroying two-thirds of the circumference of the calvarium and involving the right frontal, parietal, temporal and occipital bones, as well as the left parietal bone. This extensive bone lysis was associated with a large 'plaque-like' extra-axial subdural/pachymeningeal lesion extending within the soft tissues surrounding the calvarium. The cat was humanely euthanased. Post-mortem MRI was performed, which revealed a T2-weighted (T2W) hypointense subdural lesion and a T2W hyperintense circumferential extracranial lesion lining the right calvarium and left parietal bone. Histopathological analysis on a post-mortem sample of the lesion revealed a fibroblastic subtype of meningioma. Epithelial neoplastic cells were observed scattered through the meningioma, calvarium and surrounding muscular tissues, corresponding with presumed metastatic carcinoma. Relevance and novel information: To our knowledge, this is the first report of an intracranial meningioma associated with such an extensive and diffuse calvarial osteolysis in veterinary medicine. This is also the first description of presumed metastatic inclusions (adenocarcinoma in this case) inside an intracranial feline meningioma, which is a rare phenomenon known as tumour-to-tumour metastasis in human medicine.

Metastasis to the thyroid gland: a single-institution 16-year experience.

AIMS: Metastasis to the thyroid gland is a rare occurrence that may pose a diagnostic challenge. In this study, we aimed to report the clinicopathological features, immunoprofile, molecular alterations and outcome of 30 patients treated at our centre from 2003 to 2019. METHODS AND RESULTS: The most common site of the primary tumour was the kidney, followed by the lung, lower gastrointestinal tract and breast. In seven (23%) patients, the thyroid metastases were resected prior to the diagnosis of the primary tumours. Six patients (20%) had thyroid as the sole metastatic site. Three (10%) patients harboured tumour-to-tumour metastasis; 71% had a unilateral unifocal thyroid mass, which might be mistaken for a primary thyroid tumour. Among the 13 cases that were initially diagnosed at an outside hospital, four (31%) were misinterpreted as a thyroid primary. An immunohistochemical panel of thyroid follicular cell markers was most useful to differentiate primary thyroid tumours from metastasis. Molecularly, the metastasis showed alterations characteristic of the primary tumour, which may be helpful in establishing the diagnosis and primary site. Although the prognosis was poor, with a 5-year disease specific survival of 58%, a long-term cure was possible in cases with oligometastasis successfully treated with surgery. CONCLUSIONS: Metastasis to the thyroid gland is an uncommon phenomenon, with an incidence of 0.36% in all thyroid malignancies. It may present as a solitary thyroid mass before the discovery of the primary tumour, posing a diagnostic challenge. Although the overall prognosis is poor, a subset of patients with oligometastasis can be managed surgically.

Co-existence of lung carcinoma metastasis and enchondroma in the femur of a patient with Ollier disease.

Tumour-to-tumour metastasis is very unusual and has been defined as a tumour metastasis into another histologically different tumour. It is extremely rare in bone. We report a case of lung squamous cell carcinoma metastasized to an enchondroma in the femur of a patient with Ollier disease. A 60-year-old female had a history of a poorly differentiated squamous cell carcinoma of the lung. She underwent a video-assisted thoracoscopic lobectomy, and a follow-up MRI scan showed three lesions in the left distal femur and proximal tibia, which were initially interpreted as metastasis on radiology. Resection of the left proximal tibial lesion was performed, and the pathological findings were consistent with enchondroma with no evidence of metastasis. Subsequent curettage of lesions in the distal left femur revealed metastatic poorly differentiated carcinoma with foci of hyaline cartilage, which was most consistent with metastatic carcinoma in a pre-existing enchondroma. The MRI films were re-reviewed. Characteristic MRI features of enchondroma were found in the lesion in the left proximal tibia and one of the lesions in the left distal femur, while the features of the other lesion in the left distal femur included cortical destruction and extensive oedema in surrounding soft tissue, which were consistent with a malignant tumour. In addition, the enchondroma in the lateral condyle showed blurring and irregular inner margin and adjacent bone oedema, which likely represents a co-existing metastatic tumour and enchondroma. The difference in lineage was confirmed by immunohistochemistry. The final diagnosis was metastatic poorly differentiated carcinoma of the lung into a co-existent enchondroma. The diagnosis can be challenging and could be easily overlooked both radiologically and histologically. Thorough clinical and radiological information is critical for the diagnosis, and despite a very unusual event, awareness of the tumour-to-tumour metastasis phenomenon can avoid an inaccurate diagnosis by the pathologist, therefore preventing inappropriate clinical intervention.

Tumour-to-tumour metastasis: breast carcinoma to an olfactory neuroblastoma.

Tumour-to-tumour metastasis is a rare phenomenon. It occurs when a primary tumour is a recipient of a separate tumour within the same individual. We present a case of a 66-year-old woman with known breast cancer who presented with one-sided nasal symptoms. Examination and imaging revealed a unilateral polyp arising from the skull base. She underwent endoscopic polypectomy with the histology demonstrating tumour-to-tumour metastasis from a breast carcinoma to an olfactory neuroblastoma, a rare sinonasal tumour. Clinicians should be cautious of distant metastases in any patient presenting with head and neck symptoms and a known primary tumour. This is the first documented case of this type.

Tumour-to-Tumour Metastasis Phenomenon: Metastatic Prostatic Adenocarcinoma within an Anaplastic Oligodendroglioma in the Brain of a Dog.

A 10-year-old entire male French bulldog was presented following clusters of generalized tonic-clonic epileptic seizures. Neurolocalization was consistent with a lesion in the left forebrain. Magnetic resonance imaging of the brain revealed a large, ill-defined, intra-axial, space-occupying lesion at the level of the left temporal and parietal lobes, causing marked compression of the adjacent parenchyma. Computed tomography of the thorax and abdomen was consistent with disseminated metastatic disease. The dog was humanely destroyed and subjected to necropsy examination. Histological examination of the brain revealed a metastasis of prostatic carcinoma within an anaplastic oligodendroglioma in the left forebrain. To the author's knowledge, this is the first report describing clinical, imaging and histopathological features of an intracranial tumour-to-tumour metastasis in the brain of a dog.

Curious Residents of the Thyroid Gland: Two Case Reports of Colorectal Carcinoma Metastasis by Fine-Needle Aspiration Diagnosis.

BACKGROUND: The most frequent metastases to the thyroid originate in the kidney, lung or breast. Colorectal adenocarcinoma represents less than 4% of metastases to the thyroid gland. Solitary metastases of colorectal cancer with no other manifestation of disseminated cancer disease are exceedingly rare. Within the Bethesda Classification for Reporting -Thyroid Cytopathology, metastases are included in Diagnostic Categories "Suspicious for Malignancy" and "Malignant." CASES: We present 2 cases of colorectal adenocarcinoma metastatic to the thyroid gland, diagnosed by fine-needle aspiration (FNA). One metastasis occurred in normal thyroid parenchyma; the other was a tumour-to-tumour metastasis into a follicular carcinoma of the thyroid. The latter is the first published tumour-to-tumour metastasis of a colorectal carcinoma in the thyroid from which both components were diagnosed by FNA. CONCLUSION: Diagnosing a metastasis to the thyroid is challenging. On FNA, a dual cell population should raise suspicion. Immunocytochemical and molecular analysis may be helpful. Clinical information is essential in guiding specific ancillary technique panels in scant cellular material.

Tumour-to-tumour metastasis from papillary thyroid carcinoma with BRAF mutation to lung adenocarcinoma with EGFR mutation: the utility of mutation-specific antibodies.

AIMS: Tumour-to-tumour metastasis is a rare event. The aim of this study is to demonstrate the utility of mutation-specific antibodies to prove the occurrence of metastatic papillary thyroid cancer donor into lung adenocarcinoma recipient. METHODS AND RESULTS: We report the case of an 80-year-old woman who had a papillary thyroid carcinoma with a v-raf murine sarcoma viral oncogene homologue B1 mutation that metastasized into a lung adenocarcinoma with an epidermal growth factor receptor mutation. Immunohistochemical analysis with mutation-specific antibodies not only clearly revealed two components, but also revealed their gene mutation statuses. CONCLUSIONS: As a component of multimodal diagnostic tools, immunohistochemistry can avoid some pitfalls involved in the molecular diagnosis of complicated cases (such as our own) and can help to ensure that patients receive optimal treatments.

Renal cell carcinoma to haemangioblastoma metastasis: a rare manifestation of Von Hippel-Lindau syndrome.

Brain metastases are the most common intracranial malignancy in adults and may occasionally deposit within a pre-existing primary brain neoplasm. We describe, in two directly related family members, the rare occurrence of renal cell carcinoma (RCC) metastasis to haemangioblastoma (HB) in the context of Von Hippel-Lindau syndrome. Detection of this phenomenon can be marred by histological overlap between RCC and HB and therefore careful histological examination, and consideration of supportive immunohistochemistry, is required when examining all HB resections. Metastatic RCC to HB upstages a primary RCC and is clinically diagnostic of Von Hippel-Lindau syndrome.