HRAS-mutated primary thyroid malignant melanoma or medullary thyroid carcinoma with melanocytic dedifferentiation? A singular case with an ontogeny-phylogeny quandary.

Melanotic pigment in the thyroid is practically synonymous with chronic minocycline therapy and rare cases of melanotic medullary thyroid carcinoma. However, primary melanoma of the thyroid has not been reported yet. We report a rare case of a 25-year-old male with a locally aggressive thyroid mass and distant metastases at presentation. Radiologically, a 8.3×7.6-cm nodule was identified in the right thyroid lobe. Fine-needle aspiration cytology (FNAC) showed discohesive atypical plasmacytoid cells with prominent nucleoli and no cytoplasmic pigmentation. Serum calcitonin levels were normal. A trucut biopsy showed a malignant tumor with a similar cytomorphology, including marked nuclear pleomorphism. In addition, intracytoplasmic melanin was seen in <1% of cells. Tumor cells were immunonegative for AE1/AE3, TTF1, synaptophysin, and chromogranin while positive for SOX10, S100P, HMB45, and Melan A, confirming the diagnosis of malignant melanoma, without any detectable MTC component in the biopsy. An HRAS G13R mutation was detected on NGS, which, intriguingly, is a known mutation in MTC, and exceedingly rare in melanocytic lesions. No other clinically or radiologically apparent primary lesion was identified elsewhere in the patient. The unusual histology and hitherto unreported molecular findings make this case of primary thyroid melanocytic neoplasm worth reporting. Abstruse origin of melanoma cells in the thyroid gland with molecular signature suggestive of MTC in our case raises a nomenclature and management conundrum, prompting us to revisit the "ontogeny recapitulates phylogeny" theory.

Unusually Unnerved.

A 47-year-old woman had left-sided facial weakness and swelling for 2 months. These symptoms developed after chemotherapy. What is your diagnosis?

Small Cell Carcinoma of Ovary, Hypercalcemic Type (Malignant Rhabdoid Tumor of Ovary) with Loss of SMARCA4 (BRG1) Expression: Report of Two Cases.

Small cell carcinoma of the ovary, hypercalcemic type (SCCOHT) / malignant rhabdoid tumor of the ovary (MRTO) is a rare tumor affecting young women. It is frequently misdiagnosed due to overlapping morphological and immunohistochemical features with many other ovarian tumors. The prognosis of the tumors is very poor; hence an accurate diagnosis is of utmost importance. Recently, the loss of BRG1 protein by immunohistochemistry has been shown to be a useful diagnostic marker. We present here two cases of SSCOHT/MRTO, in young women 22 and 32 years of age, where several differential diagnoses were considered on morphology and immunohistochemistry but were confirmed as SCCOHT/MRTO by the demonstration of loss of BRG1. As the prognosis of SCCOHT is very dismal, and accurate diagnosis is of necessity, we recommend the inclusion of BRG1 immunohistochemistry in the diagnostic armamentarium of poorly differentiated ovarian tumors, particularly in young adults.