Hyaline globules in paucicellular leiomyomas of the gastrointestinal tract are distinct from skeinoid fibers and represent degenerating smooth muscle cells

Unusual Mesenchymal Tumors of the Lower Gastrointestinal Tract: When You Hear Hoofbeats in the Night, Do Not Forget the Zebras

INTRODUCTION

Little information about clinical presentation of mesenchymal tumors of the lower gastrointestinal (GI) tract due to their extreme heterogeneity is available for clinical management. Usually, small solitary asymptomatic polyps are accidently found during a screening colonoscopy performed for hematochezia, abdominal pain, constipation, diarrhea, and bowel obstruction. In this case series, we illustrate our experience with mesenchymal tumors of the lower GI tract, which are a group of unusual and quite challenging lesions.

CASE PRESENTATION

We retrospectively collected mesenchymal tumors of the lower GI tract in our institution (Fondazione IRCSS Ca' Granda - Ospedale Maggiore Policlinico di Milano) during the last 10 years. We reviewed the histological slides, and, when necessary, we performed immunohistochemical analyses to better characterize the tumors. A total of 99 cases were identified: 45 GISTs, 42 lipomas, 4 leiomyomas, 3 Kaposi sarcomas, 1 schwannoma, 1 ganglioneuroma, 1 hemangioma, 1 inflammatory fibroid polyp, and 1 challenging case of spindle cell melanoma. We focused on the most rare entities excluding therefore all GISTs and lipomas from re-evaluation.

CONCLUSION

Mesenchymal tumors of the lower GI tract represent a highly heterogeneous group of lesions encompassing GISTs, lipomas, smooth muscle tumors (leiomyoma and leiomyosarcoma), GI schwannomas, inflammatory fibroid polyps, solitary fibrous tumors, and other unusual spindle cell tumors. Immunohistochemistry and, in selected cases, molecular biology remain a useful tool which, in addition to a meticulous study of the morphology, helps the pathologist in the tangled jungle of differential diagnosis.

An Epithelioid Smooth Muscle Neoplasm Mimicking a Signet Ring Cell Carcinoma in the Ovary

A 53-yr-old woman who presented with elevated renal indices was discovered to have a 4.5 cm right renal mass and an incidental 9.7 cm left ovarian mass on imaging studies. She underwent a partial nephrectomy and bilateral salpingo-oophorectomy, revealing a chromophobe renal cell carcinoma and an unusual ovarian neoplasm with epithelioid cells displaying prominent signet ring cell-like morphology. Immunohistochemical analysis of the ovarian neoplasm demonstrated that the tumor cells were diffusely immunoreactive for smooth muscle markers and negative for all tested cytokeratins and epithelial membrane antigen. On the basis of these results, the tumor was interpreted as an unusual epithelioid smooth muscle neoplasm with extensive signet ring cell-like features. Along with primary ovarian signet ring stromal tumors and sclerosing stromal tumors, this example adds epithelioid smooth muscle neoplasms with unusual cytologic alterations to the list of uncommon nonepithelial tumors that can simulate metastatic signet ring cell carcinoma (Krukenberg tumor) in the ovary.

Endoscopic ultrasound-guided fine-needle aspiration cytology in the diagnosis of leiomyomas of the gastrointestinal tract

We investigated the efficiency and accuracy of endoscopic ultrasound-guided fine-needle aspiration cytology (EUS-FNAC) in the diagnosis of gastrointestinal leiomyoma (GIL). Between January 2009 and May 2018 we performed 795 EUS-FNAC studies of lesions of the gastrointestinal (GI) tract for various clinical indications. A diagnosis of GIL by cytological and cell block study was made in 14 patients (57.1% males, mean age 53.6 years, range 22-84 years). 7 tumors (50%) were detected incidentally. The lesions ranged in size from 2 to 10cm (mean size 4.4cm). The location of the tumors was: esophagus 7 (50%), stomach 6 (42.9%) and rectum 1(7.1%). The mean size of the symptomatic tumors was 5.2cm (range 3-10cm). The follow-up of the 14 patients varied from 1 to 108 months (median 39.5 months), during which no recurrence or evidence of lesion progression was observed. Imaging alone was not sufficient for an accurate diagnosis to be made. The pathological diagnosis was based on a combination of cytological, histopathological, and immunohistochemical features. The intracytoplasmic eosinophilic globule is a useful marker of paucicellular GIL differentiating it from gastrointestinal stromal tumor and leiomyosarcoma. EUS-FNAC is a reliable, accurate, and safe method for the diagnosis of GIL.

Uterine smooth muscle tumors with features suggesting fumarate hydratase aberration: detailed morphologic analysis and correlation with S-(2-succino)-cysteine immunohistochemistry

Rare, sporadic uterine leiomyomas arise in the setting of severe metabolic aberration due to a somatic fumarate hydratase mutation. Germline mutations account for the hereditary leiomyomatosis and renal cell carcinoma syndrome, which predisposes for cutaneous and uterine leiomyomas and aggressive renal cell carcinomas. Altered fumarate hydratase leads to fumarate accumulation in affected cells with formation of S-(2-succino)-cysteine, which can be detected with the polyclonal antibody. High levels of these modified cysteine residues are found characteristically in fumarate hydratase-deficient cells but not in normal tissues or tumors unassociated with hereditary leiomyomatosis and renal cell carcinoma syndrome. We hypothesized that S-(2-succino)-cysteine-positive leiomyomas, indicating fumarate hydratase aberration, have morphologic features that differ from those without S-(2-succino)-cysteine positivity. Hematoxylin and eosin-stained slides of uterine smooth-muscle tumors were prospectively analyzed for features suggesting hereditary leiomyomatosis and renal cell carcinoma syndrome, such as prominent eosinophilic macronucleoli with perinucleolar halos, yielding nine cases. Germline genetic testing for fumarate hydratase mutations was performed in three cases. A detailed morphological analysis was undertaken, and S-(2-succino)-cysteine immunohistochemical analysis was performed with controls from a tissue microarray (leiomyomas (19), leiomyosarcomas (29), and endometrial stromal tumors (15)). Of the nine study cases, four had multiple uterine smooth muscle tumors. All cases had increased cellularity, staghorn vasculature, and fibrillary cytoplasm with pink globules. All cases had inclusion-like nucleoli with perinuclear halos (7 diffuse, 1 focal). All showed diffuse granular cytoplasmic labeling with the S-(2-succino)-cysteine antibody. Two of three tested patients had germline fumarate hydratase mutations. Only one leiomyoma from the tissue microarray controls was immunohistochemically positive, and it showed features similar to other immunohistochemically positive cases. Smooth-muscle tumors with fumarate hydratase aberration demonstrate morphological reproducibility across cases and S-(2-succino)-cysteine immuno-positivity. Although the features described are not specific for the germline fumarate hydratase mutation or the hereditary leiomyomatosis and renal cell carcinoma syndrome, their presence should suggest fumarate hydratase aberration. Identifying these cases is an important step in the diagnostic workup of patients with possible hereditary leiomyomatosis and renal cell carcinoma.

Corpora amylacea in gastrointestinal leiomyomas: a clinical, light microscopic, ultrastructural and immunohistochemical study with comparison to hyaline globules

CONTEXT

Corpora amylacea (CA) are inclusions with starch-like composition that occur in various conditions. We have observed CA in gastrointestinal leiomyomas (GILM) and hypothesised that they differ from intracytoplasmic hyaline globules (HG) of GILM. We aimed to investigate the anatomical distribution, prevalence, staining characteristics and ultrastructural features of CA and compare them with HG of GILM.

DESIGN

Slides from a consecutive series of resected GILM and bland spindle cell tumours were examined for CA and HG. Special stains, electron microscopy and elemental analysis were performed on select leiomyomas.

RESULTS

CA occurred in 13/35 GILM (37%) from the following sites: oesophagus (4/8), stomach (5/7) including one frozen section, small intestine (1/2) and large intestine (3/18), but were not identified in 19 gastrointestinal stromal tumours (12 gastric, 7 small intestinal; p=0.0019), five schwannomas (three gastric, two small intestinal; p=0.154) and 35 non-GILM (p=0.0001). The densities of CA ranged from one per 4-200 mm(2). CA stained intensely with periodic acid Schiff after diastase predigestion (PASD), Alcian blue and ubiquitin, and faintly in peripheral zones for desmin and smooth muscle actin. Ultrastructurally, CA consisted of an electron-dense outer layer and a fibrillar core with scattered particle matter. HG were present in all leiomyomas, but showed variable staining for PASD, negative staining for Alcian blue and ubiquitin, and positive staining for smooth muscle markers.

CONCLUSIONS

CA are a distinctive histological feature of approximately one third of GILM with different composition to HG. These differences may represent divergent degenerative processes or different stages of a single degenerative process over time.

Intramuscular corpora amylacea adjacent to ileal low-grade neuroendocrine tumours (typical carcinoids): a light microscopic, immunohistochemical and ultrastructural study

AIMS

The purposes of this study are to (1) document the prevalence of intracytoplasmic inclusions adjacent to ileal well-differentiated neuroendocrine tumours (WNETs), (2) examine whether and how tumour and patient characteristics are associated with inclusions and (3) investigate their properties on special stains and electron microscopy in comparison with corpora amylacea (CA).

METHODS

We examined the resection slides from 26 ileal, 5 gastric and 5 rectal cases of WNET. Inclusions were readily identified with H&E staining. Histochemical, immunohistochemical and ultrastructural evaluations were performed on the block with the highest number of inclusions.

RESULTS

Intracytoplasmic inclusions occurred adjacent (<1 mm) to 15 of 26 (57.7%) ileal WNETs. Patients with and without inclusions were of similar mean ages (59.5 vs 57.4 years; p=0.88), but NETs with inclusions were larger than those without inclusions (3.3 vs 1.7 cm, p=0.03). Inclusions were neither associated with gastric (mean age=65 years, mean diameter=1.5 cm) or rectal WNETs (mean age=47.8 years, mean diameter=0.5 cm) (p=0.01), nor were they present >1 mm from ileal NETs. CA stained strongly for ubiquitin, DPAS and Alcian blue; faintly and peripherally for desmin and smooth muscle actin and negatively for calcium. Ultrastructurally, their appearance was consistent with filaments, some with cores of particle matter.

CONCLUSIONS

Our results suggest that these inclusions are virtually identical to CA and present adjacent to the majority of ileal WNET. They may be the result of a degenerative process, possibly due to chronic myocyte stress from an infiltrating slow growing tumour mass or local hormonal effects.