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Presented by Dr. Pedram Argani and prepared by Dr. Sintawat Wangsiricharoen
This is a solitary gastric mass in a patient with a distant history of melanoma.
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1. Question
This is a solitary gastric mass in a patient with a distant history of melanoma.
Correct
Answer: B. Gastrointestinal stromal tumor
Histologic Description: The morphology of this neoplasm closely resembles that of metastatic melanoma. The neoplastic cells are spindled and epithelioid, have focal intranuclear inclusions, and amphophilic cytoplasm. The neoplasm demonstrated immunoreactivity (focal) for Melan A, which furthers the overlap with melanoma. However, other melanoma markers such as HMB45 and S100 were negative. The neoplasm labeled diffusely for CD117 (which could also be seen in melanoma) but also for DOG1. Importantly, the neoplasm demonstrated loss of SDH immunoreactivity, supporting the diagnosis of a succinate dehydrogenase deficient gastrointestinal stromal tumor.
Differential Diagnosis: Melanoma should label for S100, SOX10, and/or HMB45, and would be SDH intact. Leiomyosarcoma would demonstrate immunoreactivity for muscle markers, and typically does not show the multinodular appearance seen in the current case. Paraganglioma would label for neuroendocrine markers such as synaptophysin and chromogranin. A subset of these would be SDH deficient, but paragangliomas should not typically label for CD117 or DOG1.
SDH deficient gastrointestinal stromal tumors differ from gastrointestinal stromal tumors in that they often affect children, are commonly multinodular, and associated with lymph node metastases. They have thus far been almost exclusively been reported in the stomach and their behavior is not well predicted by the conventional GIST criteria of size and mitosis.
Incorrect
Answer: B. Gastrointestinal stromal tumor
Histologic Description: The morphology of this neoplasm closely resembles that of metastatic melanoma. The neoplastic cells are spindled and epithelioid, have focal intranuclear inclusions, and amphophilic cytoplasm. The neoplasm demonstrated immunoreactivity (focal) for Melan A, which furthers the overlap with melanoma. However, other melanoma markers such as HMB45 and S100 were negative. The neoplasm labeled diffusely for CD117 (which could also be seen in melanoma) but also for DOG1. Importantly, the neoplasm demonstrated loss of SDH immunoreactivity, supporting the diagnosis of a succinate dehydrogenase deficient gastrointestinal stromal tumor.
Differential Diagnosis: Melanoma should label for S100, SOX10, and/or HMB45, and would be SDH intact. Leiomyosarcoma would demonstrate immunoreactivity for muscle markers, and typically does not show the multinodular appearance seen in the current case. Paraganglioma would label for neuroendocrine markers such as synaptophysin and chromogranin. A subset of these would be SDH deficient, but paragangliomas should not typically label for CD117 or DOG1.
SDH deficient gastrointestinal stromal tumors differ from gastrointestinal stromal tumors in that they often affect children, are commonly multinodular, and associated with lymph node metastases. They have thus far been almost exclusively been reported in the stomach and their behavior is not well predicted by the conventional GIST criteria of size and mitosis.
