Introduction: The pleomorphic hyalinizing angiectatic tumor
(PHAT) is a rare non-metastatic tumor of soft tissue
identified in 1996 (1). In adults, it generally occurs in the
subcutaneous tissue of the lower limbs, although reported
also in chest wall, buttock and arms. In the literature, only
one case of PHAT has been described in the kidney at the
level of the hilum but not involving renal pelvis or
parenchyma (2). The clinical behavior of PHAT is
characterized by a slow growth and a rate of local
recurrences higher than 50%. Metastasis has not been
reported. Case Report: A 61-year-old Caucasian obese
female with a medical history of hypertension and
hypercholesterolemia was admitted at the Emergency Unit
for recurring gross hematuria since one year, becoming more
frequent and severe in the last 3 months. Due to the severe
anemia (hemoglobin of 7.7g/dl), the patient was transfused.
Computed tomography (CT) scan revealed a parenchymal
lesion of 4 cm in diameter of the lower pole of the right
kidney. The lesion was only partially capsulated, mixed with
a well evident cystic component, in strict contact with the
lower calyx suspicious for infiltration. At cystoscopy, a clot
emerging from the right ureteral meatus was evident. Urine
cytology was negative and no imaging was indicative of
transitional upper urinary tract tumor. After written informed
consent, a right nephrectomy was performed and the patient
was discharged on the 4th day. The histological exam
revealed a partially capsulated lesion (3.7 cm in diameter)
with a pseudo-cystic structure, including hemosiderin
depositions, compressing but not invading the dilated lower
calyx. The lesion was characterized by hyalinized clusters of
thin-walled ectatic blood vessels within a stroma composed
of sheets and fascicles of spindled and pleomorphic atypical cells with intranuclear inclusions. At immunohistochemical
analysis, AE1/AE3, EMA, CD31, S100, desmin, actin of
smooth muscle, HMB45, ALK resulted negative. The lesion
was classified as a PHAT. The patient is maintained in
follow-up. Discussion: PHAT is a low-grade mesenchymal
neoplasm of uncertain lineage described in soft tissue and
characterized by diffusely infiltrative borders, although some
do have well-circumscribed margins. The immunohistostaining
for S-100 protein, actin, desmin, cytokeratin,
CD-31, factor VIII antigens or epithelial membrane antigen
are negative. To date approximately 22 cases of PHAT and
40 cases of its precursor, "early PHAT", have been described
in the world literature. At least 3 cases of PHAT were
reported to progress to high-grade myxofibrosarcoma (1). A
case of PHAT arising in the hilum of the kidney, clinically
mimicking an infiltrating tumor of the renal pelvis, has been
described in 2012 (2). Our case is the second described in
retro-peritoneum and the first of the renal parenchyma. In our
patient, a partial nephrectomy was not carried out due to the
absence of well-defined margins and apparent involvement of
the lower calyx, although not confirmed by the pathological
exam. If a partial nephrectomy is performed, a strict followup
should be considered due to the high percentage of local
recurrence characterizing the clinical behavior of PHAT (3).
1 Shi Wei et al: Complex analysis of a recurrent pleomorphic
hyalinizing angiectatic tumor of soft parts. Human
Pathology 43: 121-126, 2012.
2 Muhammad T et al: Pleomorphic hyalinizing angiectatic
tumor of renal hilum. Annals of Diagnostic Pathology 16:
489-493, 2012.
3 Folpe AL and Weiss SW: Pleomorphic hyalinizing
angiectatic tumor: analysis of 41 cases supporting
evolution from a distinctive precursor lesion. Am J Surg
Pathol 11: 1417-1425, 2004
