Background. Metastasis to parotid gland occurs mostly from skin cancers of the head and neck region. Metastatic neuroendocrine tumors to the parotid gland are rare and not well studied so far. In this study, we undertook a retrospective review of secondary neuroendocrine tumors of the parotid diagnosed in our institution. The most common entities, primary tumor locations, their clinical presentations and histopathological features were analyzed. Methods. Cases of secondary neuroendocrine tumors to parotid diagnosed from August 1995 to Jan 2021 were retrieved from our institution's pathology databases, and their clinicopathological features were reviewed. Results. About 29% (120 of 420 cases) of parotid neoplasms were malignant, including 70 cases of parotid primary malignant tumors and 50 cases of metastases to parotid glands. Among metastatic tumors to the parotid glands, squamous cell carcinoma and melanoma of the head and neck region together accounted for about 78% of the cases. Only 11 of 50 metastatic tumors to the parotid were neuroendocrine carcinomas (22%). The most common primaries were poorly differentiated neuroendocrine carcinoma of lung (5 of 11 cases), including 4 cases of small cell carcinoma and one case of large cell neuroendocrine carcinoma. The second most common secondary tumor was Merkel cell carcinoma (4 of 11 cases, 36%) including one case of direct invasion from overlying skin. Medullary carcinoma of the thyroid comprised the rest of the metastases to the parotid (2 of 11 cases, 18%). Conclusion. Our results show that metastatic neuroendocrine carcinomas to the parotid gland account for about 22% of all metastatic tumors to the organ. Lung is the most common primary neuroendocrine carcinoma location. It is not uncommon for metastatic neuroendocrine carcinoma to present as the first sign of systemic clinical manifestation. Merkel cell carcinoma is the second most common entity that metastasizes to parotid, followed by medullary carcinoma of the thyroid.

Middle ear adenomas are rare, low grade glandular neoplasms with epithelial and neuroendocrine components and with varying patterns of differentiation. Due to the rarity of this tumor, there is a dearth of publications detailing the cytological features. We herein review our institution's pathological database for cytological material between 1992 and 2022 for MEA specimens and discuss possible differential diagnoses based on clinical, pathological, and cytologic data and material.

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<b><i>Introduction:</i></b> Myeloid sarcoma (MS) is a rare extramedullary tumor consisting of blasts of granulocytic, monocytic, erythroid, or megakaryocytic lineage that disrupts the architecture of the involved tissue. MS shows vast clinical, morphologic, immunophenotypic, and genetic heterogeneity posing a diagnostic dilemma, especially in small biopsy specimens such as fine-needle aspiration (FNA) and core biopsy. The objective of this study is to highlight the morphologic features of MS in cytological preparations and investigate the efficacy of pathologist-performed rapid on-site evaluation (ROSE) in assuring accurate triage. <b><i>Methods:</i></b> A retrospective review was performed for cases of MS with concurrent cytology and ROSE results from 2006 to 2017. FNA smears and touch preparations were reviewed, and the results of ROSE, immunohistochemistry (IHC), flow cytometric immunophenotyping (FCI), cytogenetics/FISH, and histology were analyzed. <b><i>Results:</i></b> A total of 15 cases were found including 6 (40%) with monocytic morphology comprising promonocytes and monoblasts and 9 (60%) with conventional myeloblastic morphology. The most common genetic subgroup was <i>KMT2A</i>-rearranged MS (33.3%) followed by extramedullary blast crisis of chronic myeloid leukemia (26.6%). ROSE provided sufficient preliminary information and ensured the procurement of adequate tissue for histology, IHCs, FCI, and cytogenetics/FISH, leading to an accurate and complete diagnosis of MS in all cases. <b><i>Discussion/Conclusion:</i></b> MS is a rare malignancy that shows pronounced clinical, morphologic, immunophenotypic, and genetic heterogeneity that often overlaps with other neoplastic and non-neoplastic entities. Features including the presence of classic myeloblasts, promonocytes, monoblasts, nucleated red blood cells, left-shifted granulocytes, cytoplasmic granules, and pseudopods are helpful hints in cytological preparations. In the modern era where pathologists are increasingly expected to do extensive diagnostic, molecular, and therapeutic biomarker testing on tissue that is historically diminishing in size, ROSE is a highly effective tool to ensure effective triage of MS aiding in an accurate, timely, and complete diagnosis.

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