Dermatofibrosarcoma protuberans is a unique fibrohistiocytic tumour expressing CD34

CD34 immunoreactivity distinguishes between scar tissue and residual tumor in re-excisional specimens of dermatofibrosarcoma protuberans

Dermatofibrosarcoma protuberans (DFSP) is a locally aggressive tumor that often recurs after simple excision, and therefore usually requires wide surgical re-excision. It is sometimes difficult to distinguish histologically between residual tumor and scar tissue formed in response to the original biopsy. In an effort to solve this diagnostic problem, we have examined CD34 immunoreactivity in 10 primary biopsies of DFSP, 12 scars, and 7 re-excisional DFSP specimens containing residual tumor adjacent to scar tissue. In all 10 primary biopsies of DFSP, the tumor cells strongly and uniformly expressed CD34. In the 12 scars, only periadnexal cells, endothelial cells, and rare, scattered dendritic cells in the dermis were immunolabeled for CD34. In the 7 re-excisions of DFSP, the foci of residual DFSP were strongly immunolabeled, while the surrounding scar tissue was not. The pattern of CD34 immunoreactivity distinguishes DFSP from scar tissue, and thereby may permit more accurate assessment of surgical margins in re-excisional specimens of DFSP.

Rapid cytokeratin stains enhance the sensitivity of Mohs micrographic surgery for squamous cell carcinoma

BACKGROUND

Recurrence of squamous cell carcinoma (SCC) following Mohs micrographic surgery is uncommon. However, such cases do exist, presumably because of incomplete excision. Identification of single cells or small clumps of SCC tumor may be extremely difficult and can be compromised by inflammatory reaction.

OBJECTIVE

The purpose of this study was to evaluate the benefits of incorporating rapid cytokeratin (CK) stains into Mohs technique.

METHODS

Simple modification of standard immunoenzyme techniques allows keratin-specific staining to be achieved in less than 90 minutes on Mohs cryostat sections. We used the rapid labeled streptavidin biotin anticytokeratin method at the stage when no tumor was apparent by hematoxylin and eosin staining in 20 patients with large, aggressive, or recurrent invasive SCCs.

RESULTS

In eight cases, single cells or small clumps of SCC tumor were identified utilizing AE-1 monoclonal antibody. These patients subsequently underwent further surgery, including wider tumor resection, superficial parotidectomy, or postoperative radiation therapy.

CONCLUSION

The rapid CK antibody staining technique enhances the sensitivity of tumor identification in Mohs micrographic surgery, and should reduce tumor recurrence rates.

QBEND/10 (anti-CD34 antibody) in external root sheath cells and follicular tumors

The human hematopoietic progenitor cell antigen (CD34) is a cell surface protein expressed by human hematopoietic progenitor cells, vascular endothelium, and many mesenchymal tumors. Sections from six samples of normal skin and from 41 epithelial tumors of the skin were studied. Immunostaining of epithelial cells from the external root sheath below the attachment of the arrector pili muscle and above the matrix cells was noted in normal samples. Tumors derived from or differentiated toward cells of the outer sheath, especially trichilemmomas, were immunostained with QBEND/10 (anti-CD34 antibody), whereas other epithelial tumors studied were negative. CD34 could serve as a marker of outer sheath cell derivation and may well be of value in the distinction between trichilemmomas and other lesions with similar histopathological features.

Immunohistochemical comparison of cutaneous histiocytoses and related skin disorders: diagnostic and histogenetic relevance of MS-1 high molecular weight protein expression

Twenty-nine cases of Langerhans cell histiocytosis (LCH), non-Langerhans cell histiocytoses (N-LCH), non-infectious granulomas, and fibroblast-related lesions were examined with a panel of monoclonal and polyclonal antibodies on freshly frozen tissue sections to characterize the macrophage phenotype of N-LCH syndromes. MS-1 high molecular weight extracellular protein, specific for sinusoidal endothelial cells and dendritic perivascular macrophages in normal human organs, was expressed by N-LCH cells but was not found in LCH cells, epithelioid cells in sarcoidosis, or palisading histiocytes in granuloma annulare. The subcellular location of MS-1 protein, i.e., cytoplasmic vs. peripheral/extracellular, allowed discrimination of small and large (foamy or multinucleated) N-LCH cells. MS-1-positive cells, which were found intermingled in cellular dermatofibromas but not in fibrous dermatofibromas, differed from MS-1-positive N-LCH cells by their dendritic morphology, and thus rather resembled their normal dermal counterparts. A preserved functional relationship of these two MS-1-positive cell types was indicated by the fact that N-LCH and cellular dermatofibromas were the only lesions found to be highly vascularized. As expected, CD1a showed high specificity for LCH, while CD34 was predominantly expressed by fibroblast-related lesions; in cellular dermatofibromas, CD34 and MS-1 expression partially overlapped. The other antigens tested showed non-specific or overlapping patterns of expression. In conclusion, assessment of MS-1 protein expression (in addition to assessment of CD1a and CD34) promises to be of diagnostic value in the discrimination of N-LCH from related skin disorders, and it may indicate a common differentiative pathway for most N-LCH disease entities.

Dermatomyofibroma: additional observations on a distinctive cutaneous myofibroblastic tumour with emphasis on differential diagnosis

Following the very recent description of a benign plaque-like myofibroblastic tumour of the skin, known as dermatomyofibroma, we present four further cases, emphasizing its clinical features and its histological differential diagnosis. Three patients were adult females and one was a boy. Two of the lesions arose on the anterior abdominal wall, one on the shoulder, and one on the neck. Clinically, there was often close resemblance to a keloid. Follow-up revealed no evidence of recurrence after simple excision. Histologically, these were non-encapsulated but well-circumscribed, plaque-like lesions located in the reticular dermis, and composed of fascicles of monomorphic myofibroblasts, orientated parallel to the skin surface. Immunohistochemically, most of the tumour cells expressed alpha-smooth-muscle actin. The principal differential diagnosis is plaque-stage dermatofibrosarcoma protuberans. Other differential diagnoses include diffuse neurofibroma, dermatofibroma and other myofibroblastic skin tumours.

Differential expression of factor XIIIa and CD34 in cutaneous mesenchymal tumors

The histogenetic relationship amongst various dendritic cells of the dermis which may express markers including factor XIIIa (FXIIIa) or CD34 remains unclear. In this study we utilized a sensitive indirect immunoperoxidase staining technique to identify CD34 and FXIIIa, as well the monocyte/macrophage markers KP-1 and MAC 387 expression in a variety of cutaneous dermal tumors of mesenchymal origin to see if differential expression of CD34 vs FXIIIa exists. Tumors studied included dermatofibroma (DF) (N = 10), keloid (N = 9), atypical fibroxanthoma (AFX) (N = 3), and dermatofibrosarcoma protuberans (DFSP) (N = 7). DF were all composed of FXIIIa+ spindle-shaped and stellate tumor cells (mean score = 4.9 or > or = 75% FXIIIa+) as previously reported, but these cells rarely (< 10%) expressed CD34. Six of 7 DFSP were found to be > 75% CD34+ and FXIIIa negative, while one DFSP was negative for both CD34 and FXIIIa. In all DFSP, there were trapped FXIIIa+ cells which were distinct from the spindle-shaped tumor cells. AFX showed sparse populations of FXIIIa+ cells in the stroma (mean score = 1.33 or 10-25% positive), which were distinct from the atypical giant cells characteristic of these tumors. Keloid similarly contained trapped FXIIIa+ cells (mean score = 0.44 or < 5% positive) that were distinct from the spindle-shaped fibroblasts of the tumor mass. Dendritic and spindle-shaped cells within these tumors were consistently both KP-1 and Mac-387 negative, while all lesions studied were characterized by scattered round, histiocytic cells which were KP-1+ and/or Mac-387+ irrespective of tumor cell type.(ABSTRACT TRUNCATED AT 250 WORDS)