Updates in spindle cell/pleomorphic lipomas

Case report: A challenging case of mixed-variant myofibroblastoma with complex imaging and pathological diagnosis

Myofibroblastomas are benign mesenchymal tumors that frequently occur in the groin. They show variable morphology, and the differential histopathological diagnoses are broad, including lipomatous to myxoid tumors. In addition, both pathological and imaging findings may be complex, which makes diagnosis challenging. We herein present a case of a mixed-variant myofibroblastoma of the wrist in a 73-year-old woman. Considering the long clinical course of more than 20 years and the imaging findings, a benign myxoid tumor including a schwannoma was suspected; however, the histopathological findings from resected specimens suggested a diagnosis of myxofibrosarcoma. Additional histopathological findings led to a diagnosis of mixed-variant myofibroblastoma. The differential diagnosis of myofibroblastoma extends beyond imaging to pathological findings because of the number of possible variants. This case reinforces the notion that the gold standard treatment for soft tissue tumors is to perform surgery only after determining the correct diagnosis by biopsy.

Spindle Cell Lipoma and Pleomorphic Lipoma in the Head and Neck: A Comprehensive Study of Six Cases With Review of Literature

BACKGROUND

Spindle cell lipomas (SL) and pleomorphic lipomas (PL) are rare variants of lipomas, occurring predominantly in the head and neck region. Laryngeal SL/PL is very uncommon and causes obstructive symptoms needing immediate intervention. These tumors are often challenging in radiology due to the admixture of elements and the presence of adipose tissue may help in diagnosis. From a surgeon's perspective, understanding the nuances of SL/PL is paramount. Histology is the gold standard for diagnosis; however, it often causes diagnostic challenges in biopsy.  Method: A retrospective review of the clinical and pathologic features of archival cases of SL/PL was performed.

RESULTS

A total of six cases of head and neck region SL/PL were identified. The age of patients ranged from 21 to 58 years and the male-to-female ratio was 5:1. The tumors were distributed in the nape of the neck (n=3), laryngeal region (n=2), and orbit (n=1). Histology in all the cases showed a low-grade neoplasm composed of a variable amount of spindle cells and adipose tissue. The stroma was myxoid in most cases. CD34 was diffusely positive in all the cases.

CONCLUSION

SLs are a rare and uncommon variant of lipoma with a predilection in the head and neck region. They are low-grade neoplasms with a propensity to recur after years. Having knowledge of this tumor can improve surgical outcomes and better patient care.

Giant pleomorphic lipoma in patient with multiple osteochondromatosis

Pleomorphic lipomas are infrequent soft tissue tumours with pseudosarcomatous behaviour. Their polymorphism provides them certain characteristics that may resemble malignancy, which may mislead the initial diagnosis. The presented case report is a 45-year-old man with a giant growing tumour on the left cervicoscapular region initially categorised as a liposarcoma by magnetic resonance with a final confirmed diagnosis of pleomorphic lipoma after the surgical resection and the examination of the pathologist. The patient presented important functional restriction of the upper left extremity, which decreased after surgical resection, improving the quality of life.

Pleomorphic Lipoma of the Parotid Gland: A Potential Cytological Pitfall

Pleomorphic lipoma is an uncommon benign adipocytic tumor that arises from the subcutis. It has no risk of recurrence, metastasis or malignant transformation. The cytological findings of pleomorphic lipoma are often overdiagnosed as suspicious of malignancy owing to the pleomorphic morphology of the floret giant cells. We present a rare case of pleomorphic lipoma of the parotid gland which was misdiagnosed as a malignant tumor on fine needle aspiration cytology. Histopathological examination and positive expression for CD34 helped to arrive at the final diagnosis. Awareness about this rare entity will prevent overdiagnosis as a malignant tumor and unnecessary radical resections for this benign tumor.

Small biopsies in the head and neck: Bone and soft tissue

Bone and soft tissue lesions in the head and neck encompass not only a broad morphologic spectrum but also significant inherent clinicopathologic overlap. Epidemiology, radiology, and location - similar to the diagnostic assessment in other sites - are especially important considerations in the context of an established mesenchymal proliferation. Herein, the approach towards diagnosis is stratified by morphology (spindle, sarcomatoid, epithelioid, round cell), cellular lineage (fibroblastic, nerve sheath, rhabdomyogenic), and tumor grade (benign, low- to high-grade malignant) as the basis of further immunohistochemical or molecular investigation.

Intradermal Low-Fat Spindle Cell Lipoma: A Case Report

Spindle cell lipoma is a rare benign neoplasm that features a mixture of evenly aligned spindle cells, mature adipocytes, and ropey collagen. Most cases of spindle cell lipoma are found in the subcutaneous tissue, and intradermal spindle cell lipoma is rarely reported. We present a case of intradermal spindle cell lipoma in a 46-year-old female who presented with a 0.7-cm flesh-colored and dome-shaped nodule on the right temple that had developed 6 years ago. This mass was excised, and upon histopathologic examination, an unencapsulated lesion was located in the dermis, which consisted of bland spindle cells, scanty mature adipocytes, rare lipoblasts, and ropey collagen bundles with prominent basophilic myxoid stroma. Immunohistochemical staining showed diffuse positivity for CD34, negativity for the S-100 protein, and loss of retinoblastoma protein expression. Based on these features, intradermal low-fat spindle cell lipoma was diagnosed. No evidence of local recurrence was observed 4 months after excision. Intradermal low-fat spindle cell lipomas are extremely rare and can easily be mistaken for tumors that have similar clinical and histopathological findings. Herein, we report a globally rare case of an intradermal low-fat spindle cell lipoma.

Spindle cell lipoma of the floor of mouth

The patient was a man in his 60s with the gradually increasing mass in his mouth. A well-defined, elastic soft mass with a major diameter of 60 mm was found on the right floor of mouth. The magnetic resonance imaging findings showed a well-defined mass with high signal on both T1 and T2-weighted image in the right sublingual space. The mass was slightly heterogeneous inside and had a septum-like appearance. The tumor was resected with care not to damage the capsule. Histopathological findings showed mature adipocytes, spindle-shaped cells, and collagenous components. Spindle cells were CD34-positive. The tumor was diagnosed as spindle cell lipoma. The patient was followed up for 6 months with no recurrence. Spindle cell lipoma is a rare entity and this is the largest case in the oral cavity. Because there are wide variety of adipocytic tumors, the careful examination of their imaging and histopathological findings is essential.

Musculoskeletal Soft-tissue Masses

Evaluation of soft-tissue masses has become a common clinical practice indication for imaging with both ultrasound and MR imaging. We illustrate the ultrasonography and MR imaging appearances of soft-tissue masses based on the various categories, updates, and reclassifications of the 2020 World Health Organization classification.

A case of occipital spindle cell lipoma: a case report

Spindle cell lipoma (SCL) is a subtype of lipoma first defined by Enzinger; it accounts for ~1.5% of all fatty tumors. Most cases occur in the posterior neck and shoulders of middle-aged men and rarely in women or the occiput. A 41-year-old woman presented to us with complaints of a mass on her left occiput which had slowly grown in size over six years. We excised the tumor, and pathological findings confirmed the diagnosis of SCL. There was no recurrence one year after the surgery.

A case report on atypical spindle cell lipomatous tumor: A rare entity

Introduction

Atypical spindle cell lipomatous tumor (ASPLT), a separate entity for the group of benign/low grade adipocytic neoplasm that is characterized by adipocyte adequacy and the presence of lipoblast-like cells and spindle cells at varying degrees.

Case presentation

Here, we report a rare case of 60 years old male with atypical spindle cell lipomatous tumor in the anterior abdominal wall.

Discussion

Histopathology is the gold standard for establishing the diagnosis and grade of soft tissue tumor and consistent radiology-pathology correlation is essential to avoid any diagnostic pitfalls [1]. Ultrasound is preferred as an initial investigation for superficially located lesions.

Conclusion

ASPLT show a wide variety of microscopic features, and differential diagnosis is important and difficult. Recognition of morphologic clues and immunohistochemistry/molecular tests to confirm the diagnosis.

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Histopathology is the gold standard for establishing the diagnosis and grade of soft tissue tumor.

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Ultrasound is preferred as an initial investigation for superficially located lesions.

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Atypical spindle cell lipomatous tumor (ASPLT), a separate entity for the group of benign/low grade adipocytic neoplasm.

Atypical spindle cell lipomatous tumor of the tongue: A rare entity arising in an unusual location

Atypical spindle cell/pleomorphic lipomatous tumor (ASCPT) constitutes an emerging entity of lipomatous tumors. It is a benign tumor. It occurs typically in limbs and limb girdles. The occurrence in oral cavity is unusual. The diagnosis of this neoplasm is challenging. Herein, we report a case of ASCPT arising in the tongue.

A Diagnostic Dilemma in Fine-Needle Aspiration Cytology: Spindle Cell/Pleomorphic Lipoma

Pleomorphic lipoma is an uncommon, pseudosarcomatous lesion. It is characterized by the pleomorphic appearance on cytology and histology, follows a benign course, with a low rate of recurrence after complete excision, and has no risk of metastasis. Here, we describe a case of pleomorphic lipoma/spindle cell lipoma in a 41-year-old man who presented with a slow-growing mass on the inner aspect of the left thigh. On fine-needle aspiration cytology, it was reported as a cellular nerve sheath tumour followed by a wide excision sample sent for histopathological examination, which revealed spindle cells exhibiting pleomorphism with mature adipocytic cells and multinucleated floret cells in a myxoid background. It was reported as pleomorphic lipoma on histological examination.

Spindle Cell Lipoma with Ossification Mimicking Atypical Lipomatous Tumor/Well-Differentiated Liposarcoma: A Case Report

Although spindle cell lipoma (SCL) is a subtype of lipoma, the characteristics of SCL are observed in both lipomatous and non-lipomatous tumors. In this article, we present a case of SCL with ossification mimicking atypical lipomatous tumors/well-differentiated liposarcomas (ALTs/WDLs). Considering the findings of magnetic resonance imaging and needle biopsy, which exhibited ALTs/WDLs, marginal resection was performed. Histopathological findings demonstrated mature adipocytes and spindle cells without atypia and no malignant osteoid tissue in the ossified region. In addition, immunohistochemistry (IHC) showed positive staining for CD34, heterogeneous retinoblastoma protein deficiency, and negative staining for mouse double minute 2 homolog (MDM2) and cyclin-dependent kinase. Fluorescence in-situ hybridization showed negative amplification of MDM2. The final diagnosis of the tumor was established using IHC as an extremely rare SCL with ossification.

WHO classification of soft tissue tumours 2020: An update and simplified approach for radiologists

The WHO classification of soft tissue tumours categorizes the lesions based on histological differentiation. In the recent fifth edition (2020), many new entities have been introduced, based on their distinct biological behaviour, genetics and morphology. With the recent advances and better understanding of molecular genetics, several novel recurrent genetic alterations have been incorporated in this edition. These may serve as reliable diagnostic and prognostic markers for various soft tissue tumours. Though predominantly a pathologist's game; the radiologists must be aware of the recent updates to contribute towards the optimal diagnosis and management of soft tissue tumours. The imaging features of the new entities have not yet been described but are expected to be explored in the coming years. We hereby present a concise review of the updates in the recent WHO classification of soft tissue tumours. We have tried to emphasize the novel molecular genetics and their surrogate immunohistochemical markers which have brought a paradigm shift in the diagnosis, therapeutics, and prognosis of soft tissue tumours. We also present simplified diagnostic algorithms to characterize soft tissue tumours based on the clinico-radiological features.

The Rapidly Expanding Group of RB1-Deleted Soft Tissue Tumors: An Updated Review

The classification of soft tissue tumors has evolved considerably in the last decade, largely due to advances in understanding the pathogenetic basis of many of these, sometimes rare, tumors. Deletion of Retinoblastoma 1 (RB1), a well-known tumor suppressor gene, has been implicated in the tumorigenesis of a particular group of soft tissue neoplasms. This group of so-called “RB1-deleted soft tissue tumors” has been rapidly expanding in recent years, currently consisting of spindle cell/pleomorphic lipoma, atypical spindle cell/pleomorphic lipomatous tumor, pleomorphic liposarcoma, myofibroblastoma, cellular angiofibroma, and acral fibromyxoma. Most of these neoplasms, except pleomorphic liposarcoma, are considered benign entities and are mainly described in the older adult population. This article will review the currently known morphological, immunohistochemical, and molecular features of this heterogeneous group of mesenchymal tumors with an emphasis on differential diagnosis.

Fat-free pleomorphic lipoma of the buccal mucosa: An immunohistochemical study and literature review

Pleomorphic lipomas are extremely rare in the oral cavity. Due to the significant overlap of morphological findings with several benign and malignant soft tissue tumors, especially in the absence of adipocytes, the diagnosis is challenging. We reported the clinicopathological and immunohistochemical features of an uncommon case of a fat-free variant of pleomorphic lipoma in a 48-year-old female presenting clinically as a painless nodule on the buccal mucosa. Microscopically, the lesion showed atypical spindle cells, numerous floret-like giant multinucleated cells, and abundant ropey collagen fibers bundles. Immunohistochemistry showed strong positivity for vimentin and CD34. Mast cell tryptase highlighted numerous mast cells distributed throughout all tumor stroma. S-100 protein, pan-cytokeratin, desmin, α-SMA, EMA, CD68, STAT6, Bcl-2, MDM2, and CDK4 were negative. Conservative surgical excision was carried out, and no recurrence was observed after 13 months of follow-up. Careful histopathological and immunohistochemistry analysis of these lesions is recommended to ensure the correct diagnosis and provide adequate management through a conservative surgical approach. To the best of our knowledge, this is the second case of fat-free pleomorphic lipoma in the oral cavity.

The 2020 WHO Classification: What's New in Soft Tissue Tumor Pathology?

The fifth edition of the World Health Organization Classification of Tumors of Soft Tissue and Bone was published in early 2020. The revisions reflect a consensus among an international expert editorial board composed of soft tissue and bone pathologists, geneticists, a medical oncologist, surgeon, and radiologist. The changes in the soft tissue tumor chapter notably include diverse, recently described tumor types (eg, atypical spindle cell/pleomorphic lipomatous tumor, angiofibroma of soft tissue, and CIC-rearranged sarcoma), new clinically significant prognostic information for a variety of existing entities (eg, dedifferentiated liposarcoma and solitary fibrous tumor), and a plethora of novel genetic alterations, some of practical diagnostic relevance (eg, NAB2-STAT6 in solitary fibrous tumor, FOSB rearrangements in epithelioid hemangioma and pseudomyogenic hemangioendothelioma, and SUZ12 or EED mutations in malignant peripheral nerve sheath tumor, leading to loss of H3K27 trimethylation). In this review, we highlight the major changes to the soft tissue chapter in the 2020 World Health Organization Classification, as well as the new chapter on undifferentiated small round cell sarcomas, with a focus on updates in diagnostic categories, prognostication, and novel markers. Recent discoveries in molecular genetics are also discussed, particularly those of immediate utility in differential diagnosis, including protein correlates detectable using immunohistochemistry.

Transoral robotic resection of unusual spindle cell/pleomorphic lipoma of the larynx

Spindle cell/pleomorphic lipoma (SC/PL) is a subcutaneous mass usually localised on nape, shoulder or upper back. It is a benign lipogenic tumour composed of primitive CD34-positive spindle cells, floret-like multinucleated giant cells and mature adipocytes. Complete surgical excision is the optimal treatment. This unusual tumour in the larynx has only been reported in the medical literature once and was treated surgically by open approach. Actually, transoral robotic surgery (TORS) is most suitable because provides tridimensional magnified view plus a greater mobility with instruments, allowing complete and safe removal of the supraglottic mass, allowing rapid healing and recovery. We present the first case of a SC/PL of larynx managed with TORS. Four hours after surgery, the patient was able to take a soft diet and was discharged 2 h later. The follow-up showed an excellent clinical and functional outcome.

Frequent activating PIK3CA mutations in sporadic angiolipoma

BACKGROUND

Angiolipoma (AL) is considered as a lipoma variant that is characterized by the combination of mature adipocytes and capillary blood vessels diffusely distributed within the tumor. With the exception of recurrent PRKD2 mutations of uncertain pathogenetic significance, the genetic abnormalities of ALs are unknown, in the absence of any of the specific chromosomal aberrations described in other lipoma variants.

METHODS

Formalin-fixed and paraffin-embedded blocks of 13 conventional ALs and 5 cellular ALs from 17 individuals were retrieved and analyzed for mutations in exons 9 and 20 of PIK3CA by polymerase chain reaction and Sanger sequencing.

RESULTS

Activating PIK3CA mutations were identified in 14 tumors (78%). All PIK3CA-mutated samples carried the same exon 9 mutation, c.1634A>C (p.E545A). No mutation was detected in exon 20 of PIK3CA. No significant difference between PIK3CA-mutated and wild-type samples appeared to exist based on age, gender, and location of the tumor. All 5 cellular ALs carried the p.E545A PIK3CA mutation.

CONCLUSION

The high frequency of the p.E545A PIK3CA mutation in both conventional and cellular ALs suggests that activation of the PI3K/AKT pathway plays a key role in AL pathogenesis and reinforces the concept that cellular AL should be regarded as a variant of AL.

Chromosomal microarray analysis of benign mesenchymal tumors with RB1 deletion

Spindle cell lipomas/pleomorphic lipomas, mammary-type myofibroblastomas, and cellular angiofibromas are benign mesenchymal tumors that demonstrate histologically overlapping features but with varying anatomic locations and an uncertain etiologic relationship. These tumors have also been found to have an overlapping molecular profile with shared 13q14 deletions, which is the location of the tumor suppressor gene RB1 that encodes the retinoblastoma protein. Molecular studies thus far have largely focused on the RB1 locus, using primarily immunohistochemistry and fluorescence in situ hybridization to characterize RB1 status. However, further characterization of the molecular profile of these lesions, including genome-wide copy number variation, remains to be well defined. The goal of this study is to further characterize the specific RB1 deletions seen in spindle cell lipomas/pleomorphic lipomas, cellular angiofibromas, and mammary-type myofibroblastomas as well as to evaluate these neoplasms for additional molecular abnormalities using the OncoScan™ CNV Plus Assay, which is used for clinical use as a whole-genome copy number microarray-based assay. Ten of eleven cases demonstrated deletion of the RB1 gene with varying deletion size and breakpoints. The majority of additional genetic alterations were chromosomal losses and loss of heterozygosity with rare chromosomal gains. Although only a small subset of mesenchymal neoplasms was evaluated, the principle of creating a novel pairing of the molecular method with the tumor type represents a promising avenue for further study in a variety of tumors.

Conjunctival Stromal Tumor: Report of 2 New Cases and Review of the Literature

Conjunctival stromal tumor (COST) is an emerging entity with only a limited number of cases reported in the literature. In this report, we describe 2 additional cases, review the accumulative clinical and histopathological features and expand on the immunophenotypic property of this entity. COST appears to have a sporadic presentation, affecting both sexes and patients of variable ethnicity and age group and predominantly occurring on the bulbar conjunctiva as a slow-growing asymptomatic or slightly tender mass-like lesion. Histopathologically, COST is characterized by singly dispersed spindle to round cells, often with some degree of degenerative nuclear atypia, within a myxomatous to collagenous stroma. Lesional cells are characteristically positive for CD34 and vimentin, negative for S100, SOX10 and STAT6 and show a normal pattern of staining with RB1 by immunohistochemistry. The reported cases to date have shown an indolent biological behavior, reliably treated by a complete surgical excision.

Atypical spindle cell/pleomorphic lipomatous tumor

Atypical spindle cell/pleomorphic lipomatous tumor (ASPLT) is a recently described morphologically low-grade and clinically indolent adipocytic tumor, which will be incorporated as a new tumor entity in the upcoming 5th edition of the WHO Classification of Soft tissue and Bone tumors. Histologically, ASPLTs are characterized by ill-defined tumor margins and the presence of variable proportions of mild-to-moderately atypical spindle cells, adipocytes, lipoblasts, pleomorphic multinucleated cells and a myxoid or collagenous extracellular matrix. ASPLTs can show a wide variety of microscopic appearances and there is histologic overlap with diverse mimics. The diagnosis of ASPLT can therefore be challenging. Molecular studies have shown a consistent absence of MDM2 or CDK4 amplification. On the other hand, deletions or losses of 13q14, including RB1, have been identified in a significant subset of cases. This review provides an overview of the currently known clinical and pathological features of ASPLTs, detailing its most relevant differential diagnoses.

Exceptionally large, atypically located spindle cell lipoma

Spindle cell lipomas are a rare subtype of lipoma typically occurring in the shawl region of middle-aged men with a characteristic histological appearance consisting of mature adipocytes, ropey collagen and spindle cells. Those of extraordinary size or atypical anatomic location require a proper immunohistological workup to rule out more ominous malignancy. The authors report the rare presentation of a 54-year-old man with a large mass of the left palm causing discomfort and paresthesia for 6 months. Radiographs showed a radiolucent mass without mineralisation or bony involvement. MRI demonstrated a non-contrast-enhancing homogeneous lipomatous mass encompassing flexor tendons of the palm. Elective excisional biopsy and immunohistological analysis were consistent with spindle cell lipoma measuring 11 cm × 7 cm × 4 cm. This case is the largest spindle cell lipoma of the hand reported in the literature and appears to be the largest described in the upper extremity.