Prostatic Fibromyxoid Lesion in an Adult

Specimen Type:

Prostate

History:

A 59-year-old man with elevated serum PSA underwent prostate needle biopsies. Representative cross-sections were submitted.

Pathologic Features:

Sections revealed a lesion consisting of a mixture of hypercellular stroma, with a perivascularly distributed inflammatory infiltrate and myxoid stromal background with spindle shaped cells (Fig. 1, 2, 3). These spindle cells were negative for PSA, S-100, and desmin; vimentin was positive (Fig. 4). Inflammatory cells showed positive staining for CD68.

Differential Diagnosis:

  • Myxoid Malignant Fibrous Histiocytoma (Fig. 5)
  • Postoperative spindle cell nodule
  • Myxoid leiomyosarcoma (Fig. 6)
  • Inflammatory pseudotumor
  • Myxoid rhabdomyosarcoma
  • matoid carcinoma (Fig. 7)

Myxoid Malignant Fibrous Histiocytoma: (Fig. 5) HE 400X This has become one of the most common malignant sarcomas of older adults. It tends to occur in the deep soft tissue of the extremities and the retroperitoneum. However, it has been described in nearly every organ of the body. Signs and symptoms relate directly to the location in which it arises. It is a diagnosis of exclusion; the burden of proof is upon the pathologist to do a battery of immunohistochemical studies to exclude other sarcomas. Several histologic variants are described (storiform-pleomorphic, myxoid, inflammatory, giant cell, and angiomatoid). In general, all of these tumors follow an aggressive course and will recur unless widely excised.

Postoperative spindle cell nodule: Postoperative spindle cell nodules are easily identified by the history of previous manipulation of the prostate gland. The nodule consists of a reactive proliferation of spindle cells occurring up to several months after a lower genitourinary tract procedure, such as transurethral resection or biopsy. Because of the potential for inappropriate treatment the clinician must be aware of this entity so that he might question the diagnosis and raise the possibility of a postoperative spindle cell nodule whenever sarcoma is diagnosed after recent surgical instrumentation for a nonmesenchymal lesion in the genitourinary tract.

Myxoid leiomyosarcoma: (Fig. 6) HE 400X Leiomyosarcoma is the second most common sarcoma after rhabdomyosarcoma among all prostatic sarcomas . Leiomyosarcoma of the prostate presents as a large bulky mass that replaces most of the prostate. Patients range in age from 40 to 71 years (mean, 59 years). The histologic findings are typical of leiomyosarcoma at other sites. Tumor cells display intense cytoplasmic immunoreactivity for SMA (Smooth Muscle Actin) and vimentin and weak desmin positivity. Most are negative for cytokeratin. Local recurrence and distant metastasis are frequent and the prognosis is poor. Radical surgery is the preferred treatment, although limited data are available.

Inflammatory pseudotumor: Nodular spindle cell proliferations without preceding surgery have been described in patients ranging in age between 16 and 75 years. They may reach a size of 8 cm in diameter, which is much larger than in postoperative spindle cell nodules. Histologically, the stroma is loose, edematous and myxoid, with abundant small slit like blood vessels resembling granulation tissue. Mitotic figures are infrequent. The spindle sells are positive for vimentin and rarely stain for SMA, desmin and keratin; S-100 protein and myoglobin are negative. The lesion is diploid with a benign behavior.

Myxoid rhabdomyosarcoma: Rhabdomyosarcoma of the prostate has a peak incidence between birth and 6 years of age, although sporadic cases have been reported in elderly patients. Serum PSA and PAP are normal. The tumor is extensive (mean diameter of 5 to 9 cm). Most are embryonal rhabdomyosarcoma and the remainder are alveolar, botryoid, and spindle cell subtypes. The tumor cells may display immunoreactivity for desmin, myogenin, myoglobin, and vimentin. All tumors are aneuploid. Combination chemotherapy in conjunction with surgery and radiotherapy has improved patient outcome in the past 2 decades.

Diagnosis:

Inflammatory Pseudotumor of the Prostate

Key Features:

  • Synonym: Pseudosarcomatous Fibromyxoid Tumor
  • Rare, may resemble sarcoma or sarcomatoid carcinoma
  • Similar to postoperative spindle cell nodule but without history of TURP or biopsy
  • Macro: Mean tumor size is 3.6 cm but can reach 8 cm
  • Micro:
    • myxoid lesion with a proliferation of spindle fibroblastic cells
    • background of granulation tissue type vascularity and inflammatory
    • infrequent mitoses
    • absence of atypical cells
  • Spindle cells: Vimentin + ; PSA, PAP - ; SMA, Desmin , keratin : rarely + ; S-100 and myoglobin : -
  • Inflammatory cells: CD68 +
  • Benign behavior

Table 1: Differential diagnosis of myxoid lesions of the prostate

Courtesy of Dr. KA Iczkowski

  • IHC: immunohistochemical
  • SMA: Smooth Muscle Actin

References:

  1. Helpap B. Nonepithelial tumor-like lesions of the prostate: a never-ending diagnostic problem. Virchows Arch. 2002 Sep;441(3):231-7. Epub 2002 Jul 5.
  2. Iczkowski KA, Shanks JH, Gadaleanu V, Cheng L, Jones EC, Neumann R, Nascimento AG, Bostwick DG. Inflammatory pseudotumor and sarcoma of urinary bladder: differential diagnosis and outcome in thirty-eight spindle cell neoplasms. Mod Pathol. 2001 Oct;14(10):1043-51.
  3. Cespedes RD, Lynch SC, Grider DJ. Pseudosarcomatous fibromyxoid tumor of the prostate. A case report with review of the literature. Urol Int. 1996;57(4):249-51.
  4. Ro JY, el-Naggar AK, Amin MB, Sahin AA, Ordonez NG, Ayala AG. Pseudosarcomatous fibromyxoid tumor of the urinary bladder and prostate: immunohistochemical, ultrastructural, and DNA flow cytometric analyses of nine cases. Hum Pathol. 1993 Nov;24(11):1203-10.