Cytopathologic features of olfactory neuroblastoma

BACKGROUND. Olfactory neuroblastoma (ONB) is an uncommon neoplasm arising from the olfactory mucosa. Because its cytopathology is largely limited to case reports, the goal was to evaluate a series of ONB cases, compare them with previously reported cases, and with a control group of pulmonary and cutaneous small cell neuroendocrine carcinoma (NEC). METHODS. Six fine-needle aspiration (FNA) biopsies of metastatic ONB and one case with imprint smears of primary ONB were recovered from files. Aspirates from seven FNA cases of metastatic pulmonary small cell NEC and four cases of metastatic Merkel cell carcinoma to the head and neck functioned as a control group and were compared with those of ONB. RESULTS. Seven cases from 4 patients included 3 males (ages 33-39 yrs) and 1 female (age 58 yrs). Aspirates were acquired from Soft tissues of the neck (three cases), cervical lymph nodes (two cases), parietal scalp (one case), and imprint of a nasal mass (one case). A correct cytologic diagnosis of metastatic ONB (five cases) or malignant small round cell tumor (one case) was made in six cases. One aspirate was misdiagnosed as a reactive lymph node. The single primary tumor and five of six metastatic tumors were histologically confirmed. Cytologic features were similar in all cases. These included high cellularity (seven of seven cases), distribution as single forms and cell Clusters (seven of seven cases), a two-cell population of intact and apoptotic nuclei (seven of seven cases), nuclear molding (seven of seven cases), paranuclear 'blue bodies' (five of seven cases), necrosis (five of seven cases), and absence of lymphoglandular bodies (seven of seven cases). Unlike prior reports, no case exhibited rosettes or fibrillar neuropil on smears. All examples from the control group displayed nearly identical cytomorphologic features to those of the study group. CONCLUSIONS. The cytopathology of metastatic ONB is nonspecific unless fibrillar neuropil is identified. Nonetheless, a cytopathologic diagnosis of metastatic ONB can be made with confidence in nearly all patients if a well documented history of ONB exists. Minus Such a clinical context, aspirates of metastatic ONB may be mistaken for metastatic pulmonary small cell NEC, cutaneous neuroendocrine (Merkel cell) carcinoma, and even small cell lymphoma.