Mesenchymal neoplasms of the tubular gut and adjacent structures: experience with EUS-guided fine-needle aspiration cytopathology

Cytopathology of rare gastric mesenchymal neoplasms: A series of 25 cases and review of literature

BACKGROUND

Gastrointestinal stromal tumour (GIST) is the most common mesenchymal neoplasm arising in the stomach. However, a number of other rare mesenchymal neoplasms do occur at this anatomic site, which often presents a diagnostic challenge for cytopathologists on endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA). Our study aims to selectively present the clinico-radiological and cytopathological characteristics of these rare "non-GIST" neoplasms, as well as their differential diagnoses.

MATERIAL AND METHODS

We performed a 20 year retrospective search in the cytopathology database of our two large medical institutions for non-GIST mesenchymal neoplasms arising in the stomach and diagnosed on EUS-FNA. Data regarding the patients' demographics and radiological findings were analysed. All available cytopathology specimens were reviewed. The cytomorphological characteristics and the accompanying immunohistochemical stains, when available, were subsequently analysed.

RESULTS

Twenty-five cases of gastric mesenchymal tumours were selectively included in the study after excluding all cases of GIST (n = 113) diagnosed on FNA. These cases included 10 leiomyomas (40%), eight schwannomas (32%), five glomus tumours (20%), one perivascular epithelioid cell neoplasm, and one desmoid tumour. The specimen cellularity was variable and ranged from hypocellular to highly cellular. Most smears were composed of spindle cells with a few showing epithelioid morphology. Cell blocks were available in 20 cases and a range of immunohistochemical ancillary studies were performed. DOG-1, c-KIT, smooth muscle actin (SMA), and S100-protein were the most common immunomarkers done.

CONCLUSION

Our study highlights important cytomorphological characteristics of rare mesenchymal neoplasms arising in the stomach. In the appropriate clinical setting and with the help of immunohistochemistry, an accurate diagnosis of these neoplasms can be achieved.

Cytopathology of solitary fibrous tumor: a series of 34 cases

INTRODUCTION

Solitary fibrous tumor (SFT), a fibroblastic neoplasm characterized by a specific genetic alteration (NAB2-STAT6 fusion) and relatively specific immunohistochemical profile (STAT6/CD34 positivity), is seldom the subject of cytopathology data. We report our experience with scrape smears and fine-needle aspiration (FNA) biopsies of SFT in a large patient cohort.

MATERIALS AND METHODS

A search was made of our cytopathology and surgical pathology databases for cases diagnosed as solitary fibrous tumor (SFT). FNA biopsy smears, imprint smears, and cell blocks were performed and examined using standard technique.

RESULTS

Thirty-four cases from 30 patients (M:F = 1.1:1; age range: 24-86 years, x = 58 years) met inclusion criteria for this study. All patients had prior or subsequent tissue confirmation of SFT. Twenty-seven (79%) specimens were FNAs, and 7 (21%) were scrape smears. Most cases (29, 85%) represented primary tumors, 4 (12%) were metastatic deposits, and 1 (3.5%) was a locally recurrent neoplasm. Sites included: pleura/lung 9 (26%), head/neck 8 (24%), lower extremity 7 (21%), trunk 4 (12%), intra-abdominal 3 (9%), upper extremity 2 (7%), and mediastinum 1 (4%). Mean tumor size was 7.2 cm (range: 1.5-19 cm). Three (9%) cases were diagnosed specifically as SFT. Remaining diagnoses were spindle cell neoplasm/proliferation 14 (41%), nondiagnostic 5 (15%), specific type of sarcoma 3 (9%), malignant round cell tumor 2 (6%), sarcoma 2 (6%), malignant tumor 2 (6%) and single cases of melanoma, pleomorphic adenoma, and mesenchymal tumor. Immunohistochemical (IHC) testing was performed in 7 of 27 (26%) cell blocks.

CONCLUSION

SFT FNA cytopathology is morphologically ambiguous, overlapping with a broad array of other spindle cell proliferations. A specific diagnosis is only possible with added staining of STAT6 coupled with a set of other IHC markers.

Immunocytochemistry for diagnostic cytopathology-A practical guide

Cytological specimens, which are obtained by minimally invasive methods, are an excellent source of diagnostic material. Sometimes they are the only material available for diagnosis as well as for prognostic/predictive markers. When cytomorphology is not straightforward, ancillary tests may be required for a definitive diagnosis to guide clinical management. Immunocytochemistry (ICC) is the most common and practical ancillary tool used to reach a diagnosis when cytomorphology is equivocal, to differentiate entities with overlapping morphological features, and to determine the cell lineage and the site of origin of a metastatic neoplasm. Numerous immunomarkers are available, and some are expressed in multiple neoplasms. To rule out entities within a differential diagnosis, the use of more than one marker, sometimes panels, is necessary. ICC panels for diagnostic purposes should be customised based on the clinical context and cytomorphology, and the markers should be used judiciously to preserve material for additional tests for targeted therapies in the appropriate setting. This review offers a practical guide for the use of ICC for diagnostic cytopathology, covering the most commonly encountered non-hematolymphoid diagnostic scenarios in various body sites.

Cytopathology of myxoinflammatory fibroblastic sarcoma: a series of eight cases and review of the literature

INTRODUCTION

Myxoinflammatory fibroblastic sarcoma (MIFS) is a rare low-grade sarcoma presenting as a slow-growing mass that occurs mainly in the distal extremities of adults. Relatively little is known about the cytopathology of MIFS. We evaluated cytologic characteristics of MIFS on fine-needle aspiration (FNA).

MATERIALS AND METHODS

A search was made of our cytopathology and surgical pathology databases for cases diagnosed as MIFS. FNA biopsy smears and cell-block were performed and examined using standard technique.

RESULTS

Eight cases were retrieved from patients aged 22-90 years (mean, 56 years), and M:F ratio of 1:1. Six tumors (75%) were primary, and 2 (25%) locally recurrent. Distal lower limb was involved in all but one case (88%). One (13%) recurrent case was correctly diagnosed cytologically as MIFS; remaining single diagnoses were varied: myxofibrosarcoma, low-grade sarcoma, malignant neoplasm, myxoid neoplasm, atypical fibrohistiocytic neoplasm, atypical cells with chronic inflammation, and spindle cells with atypia. Among 7 cases with available cytologic slides for review, common features were spindle cells with variable atypia (100%), rare virocyte/Reed-Sternberg -like cells (86%), background mixed inflammation (71%), and variable myxoid stroma (57%). Pseudolipoblasts and multinucleated giant cells were rare. Hemosiderin and branching capillaries were largely absent. Immunohistochemistry was non-specific.

CONCLUSION

MIFS was accurately interpreted in only 13% of cases; remaining cases were diagnosed as atypical or malignant, which would lead to proper management. A specific cytologic diagnosis of MIFS using FNA is extremely difficult in our experience due to an absence of distinctive cytomorphology and specific immunophenotype.