Indian Journal of Pathology and Microbiology

: 2013  |  Volume : 56  |  Issue : 3  |  Page : 321--323

Pleomorphic hyalinizing angiectatic tumor exhibiting intricate branching vasculature: An interesting pattern in a rare tumor

Bharat Rekhi, Seema Aggarwal 
 Department of Pathology, Tata Memorial Hospital, Parel, Mumbai, Maharashtra, India

Correspondence Address:
Bharat Rekhi
Department of Pathology, 8th Floor, Annex Building, Tata Memorial Hospital, Dr. E.B. Road, Parel, Mumbai - 400 012, Maharashtra

How to cite this article:
Rekhi B, Aggarwal S. Pleomorphic hyalinizing angiectatic tumor exhibiting intricate branching vasculature: An interesting pattern in a rare tumor .Indian J Pathol Microbiol 2013;56:321-323

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Rekhi B, Aggarwal S. Pleomorphic hyalinizing angiectatic tumor exhibiting intricate branching vasculature: An interesting pattern in a rare tumor . Indian J Pathol Microbiol [serial online] 2013 [cited 2022 Aug 16 ];56:321-323
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A 63-year-old lady presented with a history of a painless lump on the lateral side of her left lower leg since 3-4 years that became painful over the last 10 days. She underwent a surgical resection, elsewhere and the paraffin blocks and slides were submitted for a review.

Gross findings revealed a skin covered soft-tissue mass measuring 4 × 3 × 3 cm. Cut surface was cystic and hemorrhagic. Conventional H and E stained sections showed an ill-circumscribed tumor, predominantly composed of several thickened, thrombosed blood vessels, confluent at places, lined by hyalinized fibrinous material that extended into the stroma. Interspersed were spindle cells, exhibiting focally moderate to marked nuclear atypia, including pleomorphic forms with intranuclear inclusions. Focal myxoid areas and fatty areas were noted. In addition, hemosiderin pigment was noted in histiocytes and some spindly cells. At places, mostly in peripheral areas of the tumor there was an intricate network of numerous, capillary sized, non-hyalinized blood vessels along with scattered inflammatory cells, including mast cells. There were no mitotic figures or tumor necrosis. The tumor was seen infiltrating adjacent fat [Figure 1]. Diagnosis of pleomorphic hyalinizing angiectatic tumor (PHAT) was made.

Further on immunohistochemistry (IHC), tumor cells were diffusely positive for vimentin and showed diffuse cytoplasmic positivity for acluster of differentiation (CD)99/MIC2. CD34 highlighted the blood vessels and the characteristic branching tumor vasculature [Figure 2]. S100-P was negative.{Figure 1}{Figure 2}

Prussian blue staining highlighted hemosiderin granules within spindly cells and macrophages. In view of lack of sections from margins, comments regarding margins could not be made.

PHAT of soft parts, first described by Smith in 1996, is a rare soft-tissue neoplasm. [1],[2] Its rarity is compounded with a lower index of suspicion for its diagnosis. According to the World Health Organization classification of tumors, PHAT is a non-metastasizing tumor of uncertain lineage, identified in 10-89 years old individuals, without the gender predilection. It is usually slow growing, arises in the subcutaneous tissues of lower extremities, as noted in the present case of an elderly female. Other sites (34.2%) of occurrence are arm, chest wall, axillary fossa, popliteal fossa, buttock, inguinal, perineum and buccal mucosa. [2]

Clinically, these tumors are diagnosed as hematomas or vascular neoplasms. On magnetic resonance imaging, these tumors display low signal on T1-weighed and heterogeneously high signal on T2-weighed images. Careful attention toward histopathological features is necessary for an accurate diagnosis of PHAT. Apart from the classic histopathological features, noted in the present case, intricate network of proliferative non-hyalinized vessels was also observed. Some of these vessels had their walls permeated by numerous small capillaries. Such a network of vessels has been rarely described in this tumor. Groisman et al. [3] have attributed complex capillary network as an indicator of angiogenesis, further, a possible histogenesis of this tumor with uncertain differentiation. Besides, they supported their hypothesis with vascular endothelial growth factor expression within tumor cells.

The value of correct diagnosis of PHAT is that this tumor can be erroneously over diagnosed as a high grade pleomorphic sarcoma, in view of pleomorphic cells as well as a neurilemmoma in view of hyalinized vessels. Both these entities form its differential diagnoses. Lack of significant mitoses and tumor necrosis ruled out a pleomorphic sarcoma, while lack of palisades ruled out a neurilemmoma. These features also ruled out an angiosarcoma. Presence of hemosiderin within spindly cells and macrophages can lead to hemosiderotic fibrohistiocytic lipomatous lesion (HFLL), a lesion indistinguishable from an "early" PHAT. Focal areas in the present tumor resembled HFLL, reinforcing proximity of the two lesions. [4],[5] Further on IHC, the large pleomorphic cells were vimentin and CD99 positive. CD34 highlighted the vasculature as noted earlier. S100-P negativity objectively ruled out a neurilemmoma. Noteworthy, PHAT is negative for S100-P, Keratin, epithelial membrane antigen, smooth muscle actin, desmin and CD31. [1],[2]

Local recurrences occur in 33-50% cases and at time-intervals up to 35 years after initial excision. [1],[5],[4] Although there are no cases of metastases in the literature, PHAT should be treated by wide excision whenever possible to minimize the risk of recurrence, morbidity and potential malignant progression. [1],[5],[6] The presented case was recommended follow-up.

To summarize, PHAT is a rare soft-tissue neoplasm with unique histologic and immunological features. Presence of numerous non-hyalinized vessels forming conspicuous plexiform capillary network in the present case supports that angiogenesis might play a role in the development of this rare tumor. This case report also reinforces the fact that PHAT shares morphologic proximity with HFLL.


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