CD34+ connective tissue nevi: Are they unusual?

Bioprinting of Collagen: Considerations, Potentials, and Applications

Collagen is the most abundant extracellular matrix protein that is widely used in tissue engineering (TE). There is little research done on printing pure collagen. To understand the bottlenecks in printing pure collagen, it is imperative to understand collagen from a bottom-up approach. Here it is aimed to provide a comprehensive overview of collagen printing, where collagen assembly in vivo and the various sources of collagen available for TE application are first understood. Next, the current printing technologies and strategy for printing collagen-based materials are highlighted. Considerations and key challenges faced in collagen printing are identified. Finally, the key research areas that would enhance the functionality of printed collagen are presented.

Evolution of Fibroblastic Connective Tissue Nevus in an Infant

Fibroblastic connective tissue nevus (FCTN) is a rare and recently described neoplasm of fibroblastic/myofibroblastic lineage. We report a case of a 1-month-old healthy male infant who presented with a dermal plaque on the upper chest since birth. A punch biopsy demonstrated a dermal spindle-cell neoplasm with variable smooth muscle actin positivity and negative staining for CD34, consistent with myofibroma. Over the course of the next year, the remaining lesional tissue exhibited clinical softening and a surgical excisional specimen revealed histologic findings distinct from the original biopsy. These included a poorly circumscribed proliferation of bland spindle cells arranged in short fascicles centered in the dermis and extending into the subcutis with positivity for CD34, and absence of staining with smooth muscle actin features diagnostic of FCTN. Our case allowed the opportunity to see this unusual neoplasm at different stages, and we hypothesize that FCTN may undergo an early cellular phase and that time is required for these lesions to "mature" and demonstrate the more characteristic features of FCTN.

Connective tissue nevi in children: institutional experience and review

BACKGROUND

Connective tissue nevi (CTN) are circumscribed hamartomas of the skin in which there is an abnormal mixture of normal components of the dermis that may be sporadic or associated with syndromes such as Buschke-Ollendorff, tuberous sclerosis, and Proteus.

OBJECTIVE

We sought to specify the clinical and histologic features of CTN in childhood and to propose a diagnostic approach and updated classification.

METHODS

This was a retrospective study in a tertiary pediatric outpatient population, accessing clinical and histopathological records.

RESULTS

We classified 114 cases of CTN from 1980 to 2008.

LIMITATIONS

The majority of cases were confirmed by histopathological examination. Therefore, our series excludes many CTN that were not biopsied. In addition, follow-up was variable.

CONCLUSION

Our series demonstrates the usefulness of a modified classification for CTN. Biopsy should be done when clinical diagnosis is uncertain, or in multiple lesions. When biopsy is performed it should include normal-appearing skin for comparison and, in Buschke-Ollendorff syndrome, limited anterior-posterior x-rays of the hands, wrists, feet, ankles, knees, and pelvis instead of a full skeletal survey.

Connective tissue nevi: an entity revisited

BACKGROUND

Connective tissue nevi (CTN) may be isolated, either sporadic or hereditary, or syndromic as in the Buschke-Ollendorff syndrome. Few publications have addressed the variable clinical and histopathologic expression of these benign hamartomas.

OBJECTIVE

We sought to characterize the clinical and histopathologic features of CTN and to highlight a spectrum of clinical disease.

METHODS

We carried out a retrospective study of cases selected after strict clinical and histopathologic confirmation of the diagnosis.

RESULTS

A total of 33 patients with CTN were included. The average age of onset was 2 years. Three clinical forms were distinguished: type A with lesions at a single site, with one case presenting as an ulcerated infiltrated plaque; type B with two or more sites of involvement; and type C with unusually severe infiltration with functional impairment of a limb. Histopathologic examination of lesional biopsy specimens showed 10 collagenomas, one elastoma, 18 mixed CTN, and an increased number of fibroblasts in 4 cases. No correlation between clinical type and histopathologic findings was observed.

LIMITATION

This was a descriptive case series.

CONCLUSIONS

CTN comprise a clinical spectrum ranging from isolated papules to unusually severe aggressive plaques with monomelic involvement. The histopathologic features are heterogeneous and include a newly described variant, which we name "cellular CTN" because of the increased number of fibroblasts.

CD34-positive primitive vessels and other structures in human fetuses: an immunohistochemical study

CONCLUSION

CD34-positive mesenchymal tissues are likely to play a critical role in the pattern formation of laryngeal and pharyngeal walls. In the ear, nose, and throat regions, a future clinical relevance may be found in their use for muscle repair and regeneration.

OBJECTIVES

CD34 is a well-known marker of progenitor cells of blood vessels and stromal tissues. Thus, CD34-positive cells have recently been used clinically in the field of vascular and orthopedic biotechnology because of their capacity to assist regeneration of injured tissues. However, to our knowledge, the in situ distribution of CD34-positive cells has not yet been described in the human fetus, with the exception of a few organs. The purpose of this study was to describe the location of CD34-positive cells in the head and neck regions.

METHODS

Immunohistochemistry for CD34 was carried out using seven human fetuses (12 and 15 weeks of gestation).

RESULTS

CD34-positive structures showed a vessel-like appearance and were regularly arrayed along the nasal, oral, pharyngeal, and laryngeal mucosal epithelia, whereas in the laryngeal and pharyngeal striated muscles they were distributed diffusely as fibrous tissues such as the fascia and perimysium.

CD34-positive developing vessels and other structures in human fetuses: an immunohistochemical study

CD34 is a well-known marker of progenitor cells of blood vessels and stromal tissues. Thus, CD34-positive cells have recently been used clinically in the field of vascular and orthopedic biotechnology because of their capacity to assist regeneration of injured tissues. However, to our knowledge, the in situ distribution of CD34-positive cells has not yet been described in the human fetus, with the exception of a few organs. In the present study, we conducted immunohistochemistry for CD34 using 12 human fetuses (9-15 weeks of gestation). CD34-positive structures showed a vessel-like appearance and were regularly arrayed in the viscera, nerves and lymph nodes, whereas in the body wall and extremities, they were distributed diffusely as fibrous tissues, such as the fascia and perimysium. The myocardium was also divided and bundled by CD34-positive fibrous tissues. In striated muscles, limited examples of CD34 expression were found in the tongue and extraocular muscles in which only vessels were positive. Lymphatic vessels were negative for CD34. In addition to their contribution to vascular development in any part of the body, CD34-positive mesenchymal tissues seem to play a critical role in the pattern formation of skeletal muscle, synovial tissue and other muscle/tendon-associated tissues in human fetuses.