Cytokeratin-positive fibroblastic reticular cell tumor with follicular dendritic cell features: a case report and review of the literature

Fifth Edition of the World Health Organization Classification of Tumors of the Hematopoietic and Lymphoid Tissues: Mature T-Cell, NK-Cell, and Stroma-Derived Neoplasms of Lymphoid Tissues

This review focuses on mature T cells, natural killer (NK) cells, and stroma-derived neoplasms in the fifth edition of the World Health Organization classification of hematolymphoid tumors, including changes from the revised fourth edition. Overall, information has expanded, primarily due to advancements in genomic understanding. The updated classification adopts a hierarchical format. The updated classification relies on a multidisciplinary approach, incorporating insights from a diverse group of pathologists, clinicians, and geneticists. Indolent NK-cell lymphoproliferative disorder of the gastrointestinal tract, Epstein-Barr virus-positive nodal T- and NK-cell lymphoma, and several stroma-derived neoplasms of lymphoid tissues have been newly introduced or included. The review also provides guidance on how the fifth edition of the World Health Organization classification of hematolymphoid tumors can be applied in routine clinical practice.

Extranodal Mesenteric Follicular Dendritic Cell Sarcoma Expressing Keratin Antigens: What Pitfalls Initiate Diagnostic Clues

Extranodal follicular dendritic cell sarcomas are infrequent diagnostically challenging tumors. Because of their rarity, heterogeneous histomorphologic features and variable histologic grades a significant number of extranodal lesions are prone to be misdiagnosed. Even though they have a characteristic immunoprofile, expression of a range of nonspecific markers is well documented. Even though they are typically negative for keratins, few authors have reported lesions expressing keratin. Keratin expressing tumors are more likely to be misinterpreted by pathologists further deterring their inclusion in the differential diagnosis. We report an intraabdominal mesenteric follicular dendritic cell sarcoma in a 44-year-old male that immunophenotypically expressed keratin antigens. The lesion showed a high-grade pleomorphic epithelioid appearance and the initial differential diagnosis included lymphoma, sarcomas, melanoma, and carcinomas. Follicular dendritic cell sarcoma was not considered. Expression of epithelial membrane antigen and keratin further deterred the diagnosis which was reached only after extensive use of immunomarkers. The tumor cells expressed CD21, CD23, and D2-40. Morphologically, the tumor showed some thymoma-like features with occasional TDT-expressing background T-lymphocytes. These features were hints to reconsider our differential diagnosis to include follicular dendritic cell tumors. Awareness of this aberrant staining of epithelial immunomarkers and attention to certain clues should encourage pathologists to consider this entity. Speculative assumptions may explain this unusual keratin expression in some lesions. The histomorphologic and immunohistochemical heterogeneity may suggest different variants and grades of follicular dendritic cell sarcomas. The prevalence, importance, and histogenesis of keratin expression in follicular dendritic cell sarcomas warrant further studies.

Controversies in the Spleen: Histiocytic, Dendritic, and Stromal Cell Lesions

Histiocytic, dendritic, and stromal cell lesions that occur in the spleen are challenging diagnostically, not well studied due to their rarity, and therefore somewhat controversial. New techniques for obtaining tissue samples also create challenges as splenectomy is no longer common and needle biopsy does not afford the same opportunity for examination of tissue. Characteristic primary splenic histiocytic, dendritic, and stromal cell lesions are presented in this paper with new molecular genetic findings in some entities that help differentiate these lesions from those occurring in non-splenic sites, such as soft tissue, and identify possible molecular markers for diagnosis.

A Fibroblastic Reticular Cell Tumour Arising in the Oral Cavity: A Case Report and Review of the Literature

BACKGROUND

Tumours of dendritic or histiocytic lineage are amongst the rarest tumours and probably account for < 1% of tumours affecting the lymph nodes or soft tissue. Because several of these entities were poorly recognised until recently, the true incidence is not determined.

METHODS

We present what we believe is the first reported case report of a fibroblastic reticular cell tumour arising in the oral cavity as well as reviewing the current literature regarding this rare subset of tumours.

RESULTS

We discuss the clinical and histopathological findings of our reported case and examine the literature regarding this entity. We discuss the key differential diagnoses to consider when making this diagnosis.

CONCLUSION

Histiocytic and dendritic cell derived tumours are exceptionally rare within the head and neck region although a number of these tumours have been reported within the oral cavity. We present what we believe is the first reported case of a fibroblastic reticular cell tumour arising within the oral cavity.

Nonlymphoid Hematopoietic Diseases Presenting in Bone, Soft Tissue, and Other Extranodal Sites

Context.—

Although rare in everyday practice, the initial presentation of hematopoietic neoplasms other than lymphoma in the musculoskeletal system and other extranodal sites can generate challenging diagnostic problems for surgical pathologists.

Objective.—

To review the morphologic and immunophenotypic features of various nonlymphoid hematopoietic diseases presenting at extranodal sites, with emphasis on the inherent diagnostic pitfalls and differential diagnoses of these entities to aid surgical pathologists in their accurate recognition.

Data Sources.—

Cases reviewed herein represent both in-house and consult cases seen at our institution between 2010 and 2021.

Conclusions.—

Entities that present in this way include myeloid neoplasms and histiocytic/dendritic cell neoplasms. These tumors commonly cause nonspecific symptoms, and their histologic appearance can overlap with a variety of benign neoplasms and reactive processes. This can lead to delay in diagnosis and intervention with potentially lifesaving therapy; thus, accurate and expedient recognition is of paramount importance.

Cytokeratin-positive interstitial reticulum cell (CIRC) tumor in the lymph node: a case report of the transformation from the epithelioid cell type to the spindle cell type

Background

Cytokeratin-positive interstitial reticulum cells (CIRCs), which are a subgroup of fibroblastic reticular cells (FRCs), are known to be present in the lymph nodes. There have been only a few cases of tumors derived from CIRCs.

Case presentation

We have reported a new case involving a CIRC tumor in a 75-year-old man and reviewed the literature. The resected mediastinal lymph nodes showed epithelial-like proliferation of large atypical round and polygonal epithelioid cells. The tumor cells expressed CK8, CK18, CAM5.2, AE1/AE3, epithelial membrane antigen, vimentin, fascin, and some FRC markers, which is consistent with the diagnosis of a CIRC tumor. Following chemotherapy, the CIRC tumor was observed to have responded very well and became difficult to confirm on imaging, but a small cell lung carcinoma developed 12 months later. Chemoradiotherapy was performed, but the patient passed away 29 months after the initial diagnosis. The autopsy revealed the recurrence of the CIRC tumor, residual small cell lung carcinoma, and a very small latent carcinoma of the prostate. The relapsed CIRC tumor cells had a spindle shape; they were highly pleomorphic and had invaded the superior vena cava.

Conclusion

We first reported autopsy findings of CIRC tumors and demonstrated the transformation of the tumor from the epithelioid cell type to the spindle cell type.

Spinal Cord Compression Caused by Fibroblastic Reticular Cell Tumor (FRCT) Originating from Thoracic Spine

BACKGROUND

The authors present the first reported case of a fibroblastic reticular cell tumor (FRCT) presenting with spinal cord compression. FRCTs are the rarest subset of dendritic cell tumors, a specific group of hematologic malignancies. FRCTs reportedly behave similar to low-grade sarcomas as opposed to malignant tumors.

CASE DESCRIPTION

A 45-year-old female patient presented with a 2-and-a-half week history of a flu-like illness and 1 week history of lower limb imbalance. Magnetic resonance imaging revealed an extradural lesion at T3/4 compressing the spinal cord. Initially, the patient was presumed to have metastatic spinal cord compression, and she underwent a decompressive thoracic laminectomy with debulking of the lesion with follow-up adjuvant radiotherapy. However, histology identified a unique primary FRCT originating from spine, not secondary metastatic spinal cord compression. There were no histologically aggressive features likely contributing to the favorable outcome following surgery and adjuvant radiotherapy. Her postoperative recovery was unremarkable, and she recovered fully.

CONCLUSIONS

Although rare, we report the first case of FRCT originating in the spine causing spinal cord compression. The clinical presentation of the case, histologic features of FRCT, and the treatment options are reviewed.

Histiocytic and Dendritic Cell Neoplasms

Histiocytic and dendritic cell neoplasms are very rare, belonging to a group that share morphologic, immunophenotypic, and ultrastructural characteristics of mature histiocytic/dendritic neoplasms. Histiocytic and dendritic cell neoplasms may arise de novo or in association with B-cell, T-cell, or myeloid neoplasms. Recent molecular findings, particularly the discoveries of the mutations in the RAS-RAF-MEK-ERK pathway, have greatly advanced the diagnosis and treatment options. Histiocytic and dendritic cell neoplasms may closely resemble each other, non-hematopoietic neoplasms, and even reactive processes. Therefore, it is essential to understand the clinicopathologic characteristics, differential diagnoses, and pitfalls of each entity.

Cytokeratin-positive interstitial reticulum cell tumor: recognition of a potential "in situ" pattern

Cytokeratin-positive interstitial reticulum cell (CIRC) tumor is a very rare accessory cell neoplasm of lymphoid organs derived from fibroblastic reticulum cells, which originate from mesenchymal stem cells. We describe the histologic, immunophenotypical, and molecular features of a CIRC tumor in a 67-year-old woman who underwent hysterectomy, bilateral adnexectomy, and pelvic lymphadenectomy for endometrial carcinoma. An enlarged pelvic node contained circumscribed neoplastic infiltrates in perifollicular and interfollicular areas consisting of large cells arranged in a reticular pattern with nuclear atypia, atypical mitoses, and apoptosis, but without glandular architecture or disruption of overall architecture. The atypical infiltrate coexpressed cytokeratin and vimentin, partially CD68, CD163, and lysozyme, but lacked markers of endometrial carcinoma, consistent with a diagnosis of CIRC tumor. Despite the obviously neoplastic cytological features, immunostains revealed the circumscribed and noninvasive pattern of the lesion, possibly representing an early "in situ" stage of CIRC tumor.