Thyroid plasmacytoma mimicking medullary carcinoma: A potential pitfall in aspiration cytology

Abstract

Extramedullary plasmacytoma (EMP), a malignant neoplasm of the soft tissues composed of plasma cells, may occur either as a solitary plasma‐cell tumor (primary EMP) or as a manifestation of multiple myeloma (secondary EMP). We report on the aspiration cytology findings of an intriguing case of EMP of the thyroid that was initially misinterpreted as medullary carcinoma on clinical and cytologic examination. A major contributing cause for the cytologic misinterpretation was the presence of amyloid in the aspirate and the clinical impression of a “thyroid mass.” Based on this experience, we suggest that EMP should be considered in the differential diagnosis of a neck mass that yields discohesive cells associated with amyloid/amyloid‐like material. Clinical correlation and immunocytochemistry are crucial in avoiding pitfalls in this situation. Diagn. Cytopathol. 2000;23:354–358. © 2000 Wiley‐Liss, Inc.

Extramedullary plasmacytoma of thyroid - a mimicker of medullary carcinoma at fine needle aspiration cytology: A case report

“…A similar case of solitary plasmacytoma of the thyroid has been documented in literature by Bourtsos et al .,[56] who have also demonstrated this pitfall in aspiration cytology diagnosis. Hurthle cells are notorious mimics of malignant cells.…”

Plasmacytoid morphology of poorly differentiated thyroid carcinoma: Diagnostic approach with a brief review of the literature

“…Hürthle cell variant of papillary carcinoma may show nuclear irregularity with grooving and inclusions, which help in the categorisation of the tumour. Two other haematolymphoid malignancies that can cause diagnostic confusion with the plasmacytoid PDTC are plasma cell neoplasm in the thyroid or a low‐grade marginal zone lymphoma with plasmacytic differentiation. Plasma cell neoplasm can rarely manifest as extramedullary plasmacytoma of thyroid or the more common myelomatous infiltration of thyroid.…”

Extramedullary plasmacytoma, a report of five cases diagnosed by FNAC

“…It is important to distinguish EMP at these sites from primary tumours to avoid unnecessary surgery. Because of the cytomorphological similarity between plasma cells and endocrine cells, EMP of pancreas may be confused with islet cell tumour 5 and EMP of thyroid with medullary carcinoma 9 . Similarly, rarity of EMP at a specific site along with the presence of atypical plasma cells can cause a diagnostic dilemma as described with high‐grade urothelial carcinoma of urinary bladder 10 and anaplastic seminoma of testis 11 …”

“…Approximately 90% of these tumours are found in the head and neck region commonly affecting the nasal cavity, paranasal sinuses, tonsillar fossa and oral cavity 1 . There are isolated case reports of EMP occurring in unusual locations involving almost every organ, such as pituitary, 2 gastrointestinal tract, 3 liver, 4 pancreas, 5 breast, 6 salivary gland, 7 mediastinum, 8 thyroid gland, 9 urinary bladder 10 and testis, 11 either as a primary presentation or as a metastatic deposit of MM. The clinical presentation in such cases is unique and the management complex.…”